Aprotinin
Encyclopedia
The drug aprotinin is the bovine version of the small protein basic pancreatic trypsin inhibitor, or BPTI, which inhibits trypsin
and related proteolytic enzyme
s. Under the trade name Trasylol, aprotinin was used as a medication
administered by injection
to reduce bleeding
during complex surgery
, such as heart and liver surgery. Its main effect is the slowing down of fibrinolysis
, the process that leads to the breakdown of blood clots. The aim in its use was to decrease the need for blood transfusion
s during surgery, as well as end-organ damage due to hypotension
(low blood pressure) as a result of marked blood loss. The drug was temporarily withdrawn worldwide in 2007 after studies suggested that its use increased the risk of complications or death; this was confirmed by follow-up studies. Trasylol was entirely and permanently withdrawn in May 2008, except for very restricted research use.
types arranged in a chain 58 residues long that folds into a stable, compact tertiary structure of the 'small SS-rich" type, containing 3 disulfides, a twisted β-hairpin and a C-terminal α-helix
.
The amino acid sequence for bovine BPTI is RPDFC LEPPY TGPCK ARIIR YFYNA KAGLC QTFVY GGCRA KRNNF KSAED CMRTC GGA. There are 10 positively-charged lysine (K) and arginine (R) side chains and only 4 negative aspartate (D) and glutamates (E), making the protein strongly basic
, which accounts for the basic in its name. (Because of the usual source organism, BPTI is sometimes referred to as bovine pancreatic trypsin inhibitor.)
The high stability of the molecule is due to the 3 disulfide bond
s linking the 6 cysteine
members of the chain (Cys5-Cys55, Cys14-Cys38 and Cys30-Cys51). The long, basic lysine
15 side chain on the exposed loop (at top left in the image) binds very tightly in the specificity pocket at the active site of trypsin and inhibits its enzymatic action. BPTI is synthesized as a longer, precursor sequence, which folds up and then is cleaved into the mature sequence given above.
BPTI is the classic member of the protein family of Kunitz-type serine protease inhibitors. Its physiological functions include the protective inhibition of the major digestive enzyme trypsin when small amounts are produced by cleavage of the trypsinogen precursor during storage in the pancreas.
s, specifically trypsin
, chymotrypsin
and plasmin
at a concentration of about 125,000 IU/ml, and kallikrein
at 300,000 IU/ml. Its action on kallikrein
leads to the inhibition of the formation of factor XII
a. As a result, both the intrinsic pathway of coagulation and fibrinolysis are inhibited. Its action on plasmin independently slows fibrinolysis.
, initial reports of benefit were overshadowed by concerns about toxicity.
In a meta-analysis
performed in 2004, transfusion requirements decreased by 39% in coronary artery bypass graft (CABG) surgery. In orthopedic surgery, a decrease of blood transfusions was likewise confirmed.
(a severe allergic reaction) occurs at a rate of 1:200 in first-time use, but serology
(measuring antibodies against aprotinin in the blood) is not carried out in practice to predict anaphylaxis risk because the correct interpretation of these tests is difficult.
Thrombosis
, presumably from overactive inhibition of the fibrinolytic system, may occur at a higher rate, but until 2006 there was limited evidence for this association. Similarly, while biochemical measures of renal function were known to occasionally deteriorate, there was no evidence that this greatly influenced outcomes. A study performed in cardiac surgery patients reported in 2006 showed that there was indeed a risk of acute renal failure
, myocardial infarction
and heart failure, as well as stroke
and encephalopathy
. The study authors recommend older antifibrinolytics (such as tranexamic acid
) in which these risks were not documented. The same group updated their data in 2007 and demonstrated similar findings.
In September 2006, Bayer A.G. was faulted by the FDA for not revealing during testimony the existence of a commissioned retrospective study of 67,000 patients, 30,000 of whom received aprotinin and the rest other anti-fibrinolytics. The study concluded aprotinin carried greater risks. The FDA was alerted to the study by one of the researchers involved. Although the FDA issued a statement of concern they did not change their recommendation that the drug may benefit certain subpopulations of patients. In a Public Health Advisory Update dated October 3, 2006, the FDA recommended that "physicians consider limiting Trasylol use to those situations in which the clinical benefit of reduced blood loss is necessary to medical management and outweighs the potential risks" and carefully monitor patients.
On October 25, 2007, the FDA issued a statement regarding the "Blood conservation using antifibrinolytics" (BART) randomized trial in a cardiac surgery population. The preliminary findings suggest that, compared to other antifibrinolytic drugs (epsilon-aminocaproic acid and tranexamic acid) aprotinin may increase the risk of death. On October 29, 2006 the Food and Drug Administration issued a warning that aprotinin may have serious kidney and cardiovascular toxicity. The producer, Bayer, reported to the FDA that additional observation studies showed that it may increase the chance for death, serious kidney damage, congestive heart failure and strokes. FDA warned clinicians to consider limiting use to those situations where the clinical benefit of reduced blood loss is essential to medical management and outweighs the potential risks. On November 5, 2007, Bayer announced that it was withdrawing Aprotinin because of a Canadian study that showed it increased the risk of death when used to prevent bleeding during heart surgery.
Two studies published in early 2008, both comparing aprotinin with aminocaproic acid
, found that mortality was increased by 32 and 64%, respectively. One study found an increased risk in need for dialysis and revascularisation.
No cases of bovine spongiform encephalopathy
transmission by aprotinin have been reported, although the drug was withdrawn in Italy due to fears of this.
.
In cell biology aprotinin is used as an enzyme inhibitor
to prevent protein degradation
during lysis
or homogenization
of cells and tissues.
Aprotinin can be labelled with fluorescein isothiocyanate. The conjugate retains its antiproteolytic and carbohydrate-binding properties and has been used as a fluorescent histochemical reagent for staining glycoconjugates (mucosubstances) that are rich in uronic or sialic acids.
s in 1930. and independently as a trypsin inhibitor from bovine pancreas in 1936. It was purified from bovine lung in 1964. As it inhibits pancreatic enzymes, it was initially used in the treatment for acute pancreatitis
, in which destruction of the gland by its own enzymes is thought to be part of the pathogenesis. Its use in major surgery commenced in the 1960s.
BPTI is one of the most thoroughly studied proteins in terms of structural biology
, experimental and computational dynamics, mutagenesis, and folding pathway
. It was one of the earliest protein crystal structures solved, in 1970 in the laboratory of Robert Huber
, and was the first protein to have its structure
determined by NMR spectroscopy
, in the laboratory of Kurt Wuthrich
at the ETH in Zurich in the early 1980s.
Because it is a small, stable protein whose structure had been determined at high resolution by 1975, it was the first macromolecule of scientific interest to be simulated using molecular dynamics
computation, in 1977 by J. Andrew McCammon
and Bruce Gelin, in the Karplus
group at Harvard. That study confirmed the then-surprising fact found in the NMR work that even well-packed aromatic sidechains in the interior of a stable protein can flip over rather rapidly (microsecond to millisecond time scale). Rate constants were determined by NMR for the hydrogen exchange of individual peptide NH groups along the chain, ranging from too fast to measure on the most exposed surface to many months for the most buried hydrogen-bonded groups in the center of the β sheet, and those values also correlate fairly well with degree of motion seen in the dyamics simulations.
BPTI was important in the development of knowledge about the process of protein folding
, the self-assembly of a polypeptide chain into a specific arrangement in 3D. The problem of achieving the correct pairings among the 6 Cys sidechains was shown to be especially difficult for the two buried, close-together SS near the BPTI chain termini, requiring a non-native intermediate for folding the mature sequence in vitro (it was later discovered that the precursor sequence folds more easily in vivo). BPTI was the cover image on a protein folding compendium volume by Thomas Creighton in 1992.
Trypsin
Trypsin is a serine protease found in the digestive system of many vertebrates, where it hydrolyses proteins. Trypsin is produced in the pancreas as the inactive proenzyme trypsinogen. Trypsin cleaves peptide chains mainly at the carboxyl side of the amino acids lysine or arginine, except when...
and related proteolytic enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
s. Under the trade name Trasylol, aprotinin was used as a medication
Medication
A pharmaceutical drug, also referred to as medicine, medication or medicament, can be loosely defined as any chemical substance intended for use in the medical diagnosis, cure, treatment, or prevention of disease.- Classification :...
administered by injection
Injection (medicine)
An injection is an infusion method of putting fluid into the body, usually with a hollow needle and a syringe which is pierced through the skin to a sufficient depth for the material to be forced into the body...
to reduce bleeding
Bleeding
Bleeding, technically known as hemorrhaging or haemorrhaging is the loss of blood or blood escape from the circulatory system...
during complex surgery
Surgery
Surgery is an ancient medical specialty that uses operative manual and instrumental techniques on a patient to investigate and/or treat a pathological condition such as disease or injury, or to help improve bodily function or appearance.An act of performing surgery may be called a surgical...
, such as heart and liver surgery. Its main effect is the slowing down of fibrinolysis
Fibrinolysis
Fibrinolysis is a process that prevents blood clots from growing and becoming problematic. This process has two types: primary fibrinolysis and secondary fibrinolysis...
, the process that leads to the breakdown of blood clots. The aim in its use was to decrease the need for blood transfusion
Blood transfusion
Blood transfusion is the process of receiving blood products into one's circulation intravenously. Transfusions are used in a variety of medical conditions to replace lost components of the blood...
s during surgery, as well as end-organ damage due to hypotension
Hypotension
In physiology and medicine, hypotension is abnormally low blood pressure, especially in the arteries of the systemic circulation. It is best understood as a physiologic state, rather than a disease. It is often associated with shock, though not necessarily indicative of it. Hypotension is the...
(low blood pressure) as a result of marked blood loss. The drug was temporarily withdrawn worldwide in 2007 after studies suggested that its use increased the risk of complications or death; this was confirmed by follow-up studies. Trasylol was entirely and permanently withdrawn in May 2008, except for very restricted research use.
Chemistry
Aprotinin is a monomeric (single-chain) globular polypeptide derived from bovine lung tissue. It has a molecular weight of 6512 and consists of 16 different amino acidAmino acid
Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...
types arranged in a chain 58 residues long that folds into a stable, compact tertiary structure of the 'small SS-rich" type, containing 3 disulfides, a twisted β-hairpin and a C-terminal α-helix
Alpha helix
A common motif in the secondary structure of proteins, the alpha helix is a right-handed coiled or spiral conformation, in which every backbone N-H group donates a hydrogen bond to the backbone C=O group of the amino acid four residues earlier...
.
The amino acid sequence for bovine BPTI is RPDFC LEPPY TGPCK ARIIR YFYNA KAGLC QTFVY GGCRA KRNNF KSAED CMRTC GGA. There are 10 positively-charged lysine (K) and arginine (R) side chains and only 4 negative aspartate (D) and glutamates (E), making the protein strongly basic
Base (chemistry)
For the term in genetics, see base A base in chemistry is a substance that can accept hydrogen ions or more generally, donate electron pairs. A soluble base is referred to as an alkali if it contains and releases hydroxide ions quantitatively...
, which accounts for the basic in its name. (Because of the usual source organism, BPTI is sometimes referred to as bovine pancreatic trypsin inhibitor.)
The high stability of the molecule is due to the 3 disulfide bond
Disulfide bond
In chemistry, a disulfide bond is a covalent bond, usually derived by the coupling of two thiol groups. The linkage is also called an SS-bond or disulfide bridge. The overall connectivity is therefore R-S-S-R. The terminology is widely used in biochemistry...
s linking the 6 cysteine
Cysteine
Cysteine is an α-amino acid with the chemical formula HO2CCHCH2SH. It is a non-essential amino acid, which means that it is biosynthesized in humans. Its codons are UGU and UGC. The side chain on cysteine is thiol, which is polar and thus cysteine is usually classified as a hydrophilic amino acid...
members of the chain (Cys5-Cys55, Cys14-Cys38 and Cys30-Cys51). The long, basic lysine
Lysine
Lysine is an α-amino acid with the chemical formula HO2CCH4NH2. It is an essential amino acid, which means that the human body cannot synthesize it. Its codons are AAA and AAG....
15 side chain on the exposed loop (at top left in the image) binds very tightly in the specificity pocket at the active site of trypsin and inhibits its enzymatic action. BPTI is synthesized as a longer, precursor sequence, which folds up and then is cleaved into the mature sequence given above.
BPTI is the classic member of the protein family of Kunitz-type serine protease inhibitors. Its physiological functions include the protective inhibition of the major digestive enzyme trypsin when small amounts are produced by cleavage of the trypsinogen precursor during storage in the pancreas.
Mechanism of drug action
Aprotinin inhibits several serine proteaseSerine protease
Serine proteases are enzymes that cleave peptide bonds in proteins, in which serine serves as the nucleophilic amino acid at the active site.They are found ubiquitously in both eukaryotes and prokaryotes...
s, specifically trypsin
Trypsin
Trypsin is a serine protease found in the digestive system of many vertebrates, where it hydrolyses proteins. Trypsin is produced in the pancreas as the inactive proenzyme trypsinogen. Trypsin cleaves peptide chains mainly at the carboxyl side of the amino acids lysine or arginine, except when...
, chymotrypsin
Chymotrypsin
Chymotrypsin is a digestive enzyme that can perform proteolysis. Chymotrypsin preferentially cleaves peptide amide bonds where the carboxyl side of the amide bond is a tyrosine, tryptophan, or phenylalanine. These amino acids contain an aromatic ring in their sidechain that fits into a...
and plasmin
Plasmin
Plasmin is an important enzyme present in blood that degrades many blood plasma proteins, most notably, fibrin clots. The degradation of fibrin is termed fibrinolysis. In humans, the plasmin protein is encoded by the PLG gene.- Function :...
at a concentration of about 125,000 IU/ml, and kallikrein
Kallikrein
Kallikreins are a subgroup of serine proteases, enzymes capable of cleaving peptide bonds in proteins. In humans, plasma kallikrein has no known homologue, while tissue kallikrein-related peptidases encode a family of fifteen closely related serine proteases...
at 300,000 IU/ml. Its action on kallikrein
Kallikrein
Kallikreins are a subgroup of serine proteases, enzymes capable of cleaving peptide bonds in proteins. In humans, plasma kallikrein has no known homologue, while tissue kallikrein-related peptidases encode a family of fifteen closely related serine proteases...
leads to the inhibition of the formation of factor XII
Factor XII
Coagulation factor XII also known as Hageman factor is a plasma protein. It is the zymogen form of factor XIIa, an enzyme of the serine protease class. In humans, factor XII is encoded by the F12 gene.- Function :...
a. As a result, both the intrinsic pathway of coagulation and fibrinolysis are inhibited. Its action on plasmin independently slows fibrinolysis.
Drug efficacy
In cardiac surgery with a high risk of significant blood loss, aprotinin significantly reduced bleeding, mortality and hospital stay. Beneficial effects were also reported in high-risk orthopedic surgery. In liver transplantationLiver transplantation
Liver transplantation or hepatic transplantation is the replacement of a diseased liver with a healthy liver allograft. The most commonly used technique is orthotopic transplantation, in which the native liver is removed and replaced by the donor organ in the same anatomic location as the original...
, initial reports of benefit were overshadowed by concerns about toxicity.
In a meta-analysis
Meta-analysis
In statistics, a meta-analysis combines the results of several studies that address a set of related research hypotheses. In its simplest form, this is normally by identification of a common measure of effect size, for which a weighted average might be the output of a meta-analyses. Here the...
performed in 2004, transfusion requirements decreased by 39% in coronary artery bypass graft (CABG) surgery. In orthopedic surgery, a decrease of blood transfusions was likewise confirmed.
Drug safety
There have been concerns about the safety of aprotinin. AnaphylaxisAnaphylaxis
Anaphylaxis is defined as "a serious allergic reaction that is rapid in onset and may cause death". It typically results in a number of symptoms including throat swelling, an itchy rash, and low blood pressure...
(a severe allergic reaction) occurs at a rate of 1:200 in first-time use, but serology
Serology
Serology is the scientific study of blood serum and other bodily fluids. In practice, the term usually refers to the diagnostic identification of antibodies in the serum...
(measuring antibodies against aprotinin in the blood) is not carried out in practice to predict anaphylaxis risk because the correct interpretation of these tests is difficult.
Thrombosis
Thrombosis
Thrombosis is the formation of a blood clot inside a blood vessel, obstructing the flow of blood through the circulatory system. When a blood vessel is injured, the body uses platelets and fibrin to form a blood clot to prevent blood loss...
, presumably from overactive inhibition of the fibrinolytic system, may occur at a higher rate, but until 2006 there was limited evidence for this association. Similarly, while biochemical measures of renal function were known to occasionally deteriorate, there was no evidence that this greatly influenced outcomes. A study performed in cardiac surgery patients reported in 2006 showed that there was indeed a risk of acute renal failure
Acute renal failure
Acute kidney injury , previously called acute renal failure , is a rapid loss of kidney function. Its causes are numerous and include low blood volume from any cause, exposure to substances harmful to the kidney, and obstruction of the urinary tract...
, myocardial infarction
Myocardial infarction
Myocardial infarction or acute myocardial infarction , commonly known as a heart attack, results from the interruption of blood supply to a part of the heart, causing heart cells to die...
and heart failure, as well as stroke
Stroke
A stroke, previously known medically as a cerebrovascular accident , is the rapidly developing loss of brain function due to disturbance in the blood supply to the brain. This can be due to ischemia caused by blockage , or a hemorrhage...
and encephalopathy
Encephalopathy
Encephalopathy means disorder or disease of the brain. In modern usage, encephalopathy does not refer to a single disease, but rather to a syndrome of global brain dysfunction; this syndrome can be caused by many different illnesses.-Terminology:...
. The study authors recommend older antifibrinolytics (such as tranexamic acid
Tranexamic acid
Tranexamic acid is a drug used to treat or prevent excessive blood loss during surgery and in certain other conditions...
) in which these risks were not documented. The same group updated their data in 2007 and demonstrated similar findings.
In September 2006, Bayer A.G. was faulted by the FDA for not revealing during testimony the existence of a commissioned retrospective study of 67,000 patients, 30,000 of whom received aprotinin and the rest other anti-fibrinolytics. The study concluded aprotinin carried greater risks. The FDA was alerted to the study by one of the researchers involved. Although the FDA issued a statement of concern they did not change their recommendation that the drug may benefit certain subpopulations of patients. In a Public Health Advisory Update dated October 3, 2006, the FDA recommended that "physicians consider limiting Trasylol use to those situations in which the clinical benefit of reduced blood loss is necessary to medical management and outweighs the potential risks" and carefully monitor patients.
On October 25, 2007, the FDA issued a statement regarding the "Blood conservation using antifibrinolytics" (BART) randomized trial in a cardiac surgery population. The preliminary findings suggest that, compared to other antifibrinolytic drugs (epsilon-aminocaproic acid and tranexamic acid) aprotinin may increase the risk of death. On October 29, 2006 the Food and Drug Administration issued a warning that aprotinin may have serious kidney and cardiovascular toxicity. The producer, Bayer, reported to the FDA that additional observation studies showed that it may increase the chance for death, serious kidney damage, congestive heart failure and strokes. FDA warned clinicians to consider limiting use to those situations where the clinical benefit of reduced blood loss is essential to medical management and outweighs the potential risks. On November 5, 2007, Bayer announced that it was withdrawing Aprotinin because of a Canadian study that showed it increased the risk of death when used to prevent bleeding during heart surgery.
Two studies published in early 2008, both comparing aprotinin with aminocaproic acid
Aminocaproic acid
Aminocaproic acid is a derivative and analogue of the amino acid lysine, which makes it an effective inhibitor for enzymes that bind that particular residue. Such enzymes include proteolytic enzymes like plasmin, the enzyme responsible for fibrinolysis...
, found that mortality was increased by 32 and 64%, respectively. One study found an increased risk in need for dialysis and revascularisation.
No cases of bovine spongiform encephalopathy
Bovine spongiform encephalopathy
Bovine spongiform encephalopathy , commonly known as mad-cow disease, is a fatal neurodegenerative disease in cattle that causes a spongy degeneration in the brain and spinal cord. BSE has a long incubation period, about 30 months to 8 years, usually affecting adult cattle at a peak age onset of...
transmission by aprotinin have been reported, although the drug was withdrawn in Italy due to fears of this.
In vitro use
Small amounts of aprotinin can be added to tubes of drawn blood to enable laboratory measurement of certain rapidly degraded proteins such as glucagonGlucagon
Glucagon, a hormone secreted by the pancreas, raises blood glucose levels. Its effect is opposite that of insulin, which lowers blood glucose levels. The pancreas releases glucagon when blood sugar levels fall too low. Glucagon causes the liver to convert stored glycogen into glucose, which is...
.
In cell biology aprotinin is used as an enzyme inhibitor
Enzyme inhibitor
An enzyme inhibitor is a molecule that binds to enzymes and decreases their activity. Since blocking an enzyme's activity can kill a pathogen or correct a metabolic imbalance, many drugs are enzyme inhibitors. They are also used as herbicides and pesticides...
to prevent protein degradation
Chemical decomposition
Chemical decomposition, analysis or breakdown is the separation of a chemical compound into elements or simpler compounds. It is sometimes defined as the exact opposite of a chemical synthesis. Chemical decomposition is often an undesired chemical reaction...
during lysis
Lysis
Lysis refers to the breaking down of a cell, often by viral, enzymic, or osmotic mechanisms that compromise its integrity. A fluid containing the contents of lysed cells is called a "lysate"....
or homogenization
Homogenization (biology)
Homogenization is a process that involves breaking apart cells — releasing organelles and cytoplasm.When the purpose is to extract organelles, it is frequently done in two steps; first using a blender to break the tissue up, and then with an ultrasonic or mechanical tissue disruptor. The...
of cells and tissues.
Aprotinin can be labelled with fluorescein isothiocyanate. The conjugate retains its antiproteolytic and carbohydrate-binding properties and has been used as a fluorescent histochemical reagent for staining glycoconjugates (mucosubstances) that are rich in uronic or sialic acids.
History
Initially named "kallikrein inactivator", aprotinin was first isolated from cow parotid glandParotid gland
The paired parotid glands are the largest of the salivary glands. They are each found wrapped around the mandibular ramus, and secrete saliva through Stensen's ducts into the oral cavity, to facilitate mastication and swallowing and to begin the digestion of starches.-Location:The parotid glands...
s in 1930. and independently as a trypsin inhibitor from bovine pancreas in 1936. It was purified from bovine lung in 1964. As it inhibits pancreatic enzymes, it was initially used in the treatment for acute pancreatitis
Acute pancreatitis
Acute pancreatitis or acute pancreatic necrosis is a sudden inflammation of the pancreas. It can have severe complications and high mortality despite treatment...
, in which destruction of the gland by its own enzymes is thought to be part of the pathogenesis. Its use in major surgery commenced in the 1960s.
BPTI is one of the most thoroughly studied proteins in terms of structural biology
Structural biology
Structural biology is a branch of molecular biology, biochemistry, and biophysics concerned with the molecular structure of biological macromolecules, especially proteins and nucleic acids, how they acquire the structures they have, and how alterations in their structures affect their function...
, experimental and computational dynamics, mutagenesis, and folding pathway
Protein folding
Protein folding is the process by which a protein structure assumes its functional shape or conformation. It is the physical process by which a polypeptide folds into its characteristic and functional three-dimensional structure from random coil....
. It was one of the earliest protein crystal structures solved, in 1970 in the laboratory of Robert Huber
Robert Huber
Robert Huber is a German biochemist and Nobel laureate.He was born 20 February 1937 in Munich where his father, Sebastian, was a bank cashier. He was educated at the Humanistisches Karls-Gymnasium from 1947 to 1956 and then studied chemistry at the Technische Hochschule, receiving his diploma in 1960...
, and was the first protein to have its structure
Protein structure
Proteins are an important class of biological macromolecules present in all organisms. Proteins are polymers of amino acids. Classified by their physical size, proteins are nanoparticles . Each protein polymer – also known as a polypeptide – consists of a sequence formed from 20 possible L-α-amino...
determined by NMR spectroscopy
Protein nuclear magnetic resonance spectroscopy
Nuclear magnetic resonance spectroscopy of proteins is a field of structural biology in which NMR spectroscopy is used to obtain information about the structure and dynamics of proteins. The field was pioneered by Richard R. Ernst and Kurt Wüthrich, among others...
, in the laboratory of Kurt Wuthrich
Kurt Wüthrich
Kurt Wüthrich is a Swiss chemist and Nobel Chemistry laureate.-Biography:Born in Aarberg, Switzerland, Wüthrich was educated in chemistry, physics, and mathematics at the University of Berne before pursuing his Ph.D. under the direction of Silvio Fallab at the University of Basel, awarded in 1964...
at the ETH in Zurich in the early 1980s.
Because it is a small, stable protein whose structure had been determined at high resolution by 1975, it was the first macromolecule of scientific interest to be simulated using molecular dynamics
Molecular dynamics
Molecular dynamics is a computer simulation of physical movements of atoms and molecules. The atoms and molecules are allowed to interact for a period of time, giving a view of the motion of the atoms...
computation, in 1977 by J. Andrew McCammon
J. Andrew McCammon
James Andrew McCammon is an American physical chemist known for his application of principles and methods from theoretical and computational chemistry to biological systems. A professor at the University of California, San Diego , McCammon's research focuses on the theoretical aspects of...
and Bruce Gelin, in the Karplus
Martin Karplus
Martin Karplus is an Austrian-born American theoretical chemist. He has been Theodore William Richards Professor of Chemistry at Harvard University since 1979...
group at Harvard. That study confirmed the then-surprising fact found in the NMR work that even well-packed aromatic sidechains in the interior of a stable protein can flip over rather rapidly (microsecond to millisecond time scale). Rate constants were determined by NMR for the hydrogen exchange of individual peptide NH groups along the chain, ranging from too fast to measure on the most exposed surface to many months for the most buried hydrogen-bonded groups in the center of the β sheet, and those values also correlate fairly well with degree of motion seen in the dyamics simulations.
BPTI was important in the development of knowledge about the process of protein folding
Protein folding
Protein folding is the process by which a protein structure assumes its functional shape or conformation. It is the physical process by which a polypeptide folds into its characteristic and functional three-dimensional structure from random coil....
, the self-assembly of a polypeptide chain into a specific arrangement in 3D. The problem of achieving the correct pairings among the 6 Cys sidechains was shown to be especially difficult for the two buried, close-together SS near the BPTI chain termini, requiring a non-native intermediate for folding the mature sequence in vitro (it was later discovered that the precursor sequence folds more easily in vivo). BPTI was the cover image on a protein folding compendium volume by Thomas Creighton in 1992.
External links
- The MEROPSMeropsMerops may refer to:* Merops , a genus of bee-eaters.* MEROPS, an on-line database for peptidases.It may also refer to several figures from Greek mythology:* King of Ethiopia, husband of Clymene, who lay with Helios and bore Phaethon...
online database for peptidases and their inhibitors: I02.001 - Trasylol.com (official Bayer website)