Hemoprotein
Encyclopedia
A hemeprotein or heme
protein
, is a metalloprotein
containing a heme prosthetic group- an organic compound that allows a protein to carry out a function that it cannot do alone.. Heme remains bound to the protein permanently, either covalently
or noncovalently bound
or both.
The heme contains a reduced iron atom, Fe2+ in the center of a highly hydrophobic, planar, porphyrin ring. The iron has six possible coordination bonds. The porphyrin ring has 4 nitrogen atoms that bind to the iron, leaving two other coordination positions of the iron available for bonding to the histidine of the protein and a divalent atom.
Hemeproteins probably evolved to incorporate the iron (Fe) atom contained within the protoporphyrin IX ring of heme into proteins. As it makes hemeproteins responsive to molecules that can bind divalent iron (Fe), this strategy has been maintained throughout evolution as it plays crucial physiological functions. Oxygen (O2) nitric oxide (NO), carbon monoxide (CO) and hydrogen sulfide (H2S) binds to the iron atom in heme proteins. Once bound to the prosthetic heme groups, these molecules can modulate the activity/function of those hemeproteins, affording signal transduction. Therefore, when produced in biologic systems (cells), these gaseous molecules are referred to as gasotransmitters.
Because of their diverse range of biological functions, the structural and functional characterizations of hemeproteins are the most studied classes of biomolecules. This has led to many reported literature. Therefore, for the purpose of global analysis, the data of heme protein stucture-function relationship has been united in a web-based resource, The Heme protein Database (HPD): http://heme.chem.colubmia.edu/heme.php located at a new site http://hemeprotein.info/heme.php
His-F8 of the myoglobin, also known as the proximal histadine is covalently bonded to the 5th coordination position of the iron. And as an Oxygen binds to the 6th coordination position of the iron, a distal histidine(a histidine that doesn't bond directly with the Iron), His-E7 of the myoglobin binds to the Oxygen that is now covalently bonded to the iron. The same occurs for the hemoglobin, however, being a protein with 4 subunits, the hemoglobin contains 4 heme, therefore, allowing 4 Oxygen atoms to bind to the heme.
Heme
A heme or haem is a prosthetic group that consists of an iron atom contained in the center of a large heterocyclic organic ring called a porphyrin. Not all porphyrins contain iron, but a substantial fraction of porphyrin-containing metalloproteins have heme as their prosthetic group; these are...
protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
, is a metalloprotein
Metalloprotein
Metalloprotein is a generic term for a protein that contains a metal ion cofactor. Metalloproteins have many different functions in cells, such as enzymes, transport and storage proteins, and signal transduction proteins. Indeed, about one quarter to one third of all proteins require metals to...
containing a heme prosthetic group- an organic compound that allows a protein to carry out a function that it cannot do alone.. Heme remains bound to the protein permanently, either covalently
Covalent bond
A covalent bond is a form of chemical bonding that is characterized by the sharing of pairs of electrons between atoms. The stable balance of attractive and repulsive forces between atoms when they share electrons is known as covalent bonding....
or noncovalently bound
Chemical bond
A chemical bond is an attraction between atoms that allows the formation of chemical substances that contain two or more atoms. The bond is caused by the electromagnetic force attraction between opposite charges, either between electrons and nuclei, or as the result of a dipole attraction...
or both.
The heme contains a reduced iron atom, Fe2+ in the center of a highly hydrophobic, planar, porphyrin ring. The iron has six possible coordination bonds. The porphyrin ring has 4 nitrogen atoms that bind to the iron, leaving two other coordination positions of the iron available for bonding to the histidine of the protein and a divalent atom.
Hemeproteins probably evolved to incorporate the iron (Fe) atom contained within the protoporphyrin IX ring of heme into proteins. As it makes hemeproteins responsive to molecules that can bind divalent iron (Fe), this strategy has been maintained throughout evolution as it plays crucial physiological functions. Oxygen (O2) nitric oxide (NO), carbon monoxide (CO) and hydrogen sulfide (H2S) binds to the iron atom in heme proteins. Once bound to the prosthetic heme groups, these molecules can modulate the activity/function of those hemeproteins, affording signal transduction. Therefore, when produced in biologic systems (cells), these gaseous molecules are referred to as gasotransmitters.
Because of their diverse range of biological functions, the structural and functional characterizations of hemeproteins are the most studied classes of biomolecules. This has led to many reported literature. Therefore, for the purpose of global analysis, the data of heme protein stucture-function relationship has been united in a web-based resource, The Heme protein Database (HPD): http://heme.chem.colubmia.edu/heme.php located at a new site http://hemeprotein.info/heme.php
Roles
Hemeproteins have diverse biological functions including:- Oxygen transport
- hemoglobinHemoglobinHemoglobin is the iron-containing oxygen-transport metalloprotein in the red blood cells of all vertebrates, with the exception of the fish family Channichthyidae, as well as the tissues of some invertebrates...
- myoglobinMyoglobinMyoglobin is an iron- and oxygen-binding protein found in the muscle tissue of vertebrates in general and in almost all mammals. It is related to hemoglobin, which is the iron- and oxygen-binding protein in blood, specifically in the red blood cells. The only time myoglobin is found in the...
- neuroglobinNeuroglobinNeuroglobin is a member of the vertebrate globin family involved in cellular oxygen homeostasis. It is an intracellular hemoprotein expressed in the central and peripheral nervous system, cerebrospinal fluid, retina and endocrine tissues. Neuroglobin is a monomer that reversibly binds oxygen with...
- cytoglobinCytoglobinCytoglobin is the protein product of CYGB, a human and mammalian gene.Cytoglobin is a globin molecule located in the brain and most notably utilized in marine mammals. It is thought to be a method of protection under conditions of hypoxia. The predicted function of cytoglobin is the transfer of...
- leghemoglobinLeghemoglobinLeghemoglobin is a nitrogen or oxygen carrier, because naturally occurring oxygen and nitrogen interact similarly with this protein; and a hemoprotein found in the nitrogen-fixing root nodules of leguminous plants. But nitrogen is necessary for the cycle to occur...
- hemoglobin
- CatalysisCatalysisCatalysis is the change in rate of a chemical reaction due to the participation of a substance called a catalyst. Unlike other reagents that participate in the chemical reaction, a catalyst is not consumed by the reaction itself. A catalyst may participate in multiple chemical transformations....
- peroxidasePeroxidasePeroxidases are a large family of enzymes that typically catalyze a reaction of the form:For many of these enzymes the optimal substrate is hydrogen peroxide, but others are more active with organic hydroperoxides such as lipid peroxides...
s - cytochrome c oxidaseCytochrome c oxidaseThe enzyme cytochrome c oxidase or Complex IV is a large transmembrane protein complex found in bacteria and the mitochondrion.It is the last enzyme in the respiratory electron transport chain of mitochondria located in the mitochondrial membrane...
- ligninaseLigninaseLigninase is the original term encompassing many different types of oxidative, extracellular fungal enzymes which catalyze the breakdown of lignin which is commonly found in the cell walls of plants...
s
- peroxidase
- Active membrane transportActive transportActive transport is the movement of a substance against its concentration gradient . In all cells, this is usually concerned with accumulating high concentrations of molecules that the cell needs, such as ions, glucose, and amino acids. If the process uses chemical energy, such as from adenosine...
- cytochromeCytochromeCytochromes are, in general, membrane-bound hemoproteins that contain heme groups and carry out electron transport.They are found either as monomeric proteins or as subunits of bigger enzymatic complexes that catalyze redox reactions....
s
- cytochrome
- Electron transferElectron transferElectron transfer is the process by which an electron moves from an atom or a chemical species to another atom or chemical species...
- cytochrome cCytochrome cThe Cytochrome complex, or cyt c is a small heme protein found loosely associated with the inner membrane of the mitochondrion. It belongs to the cytochrome c family of proteins. Cytochrome c is a highly soluble protein, unlike other cytochromes, with a solubility of about 100 g/L and is an...
- catalaseCatalaseCatalase is a common enzyme found in nearly all living organisms that are exposed to oxygen, where it catalyzes the decomposition of hydrogen peroxide to water and oxygen...
- cytochrome c
- SensorySensorySensory may refer to:relating to senses or smellIn biology:* Sensory preference* Sensory system, part of the nervous system of organisms* Sensory neuron, nerve cell responsible for transmitting information about external stimuli...
- FixL (Oxygen sensor)
- sGC (Nitric Oxide sensor)
- CooA (CO sensor)
- DefenseBiological defenseIn biology,*often biological defense mechanism, a form of adaptation that promotes the survivability of an organism by protecting it from its natural enemies. Also see chemical defense.In law,...
- vanabin
Hemoglobin and Myoglobin
Hemoglobin and Myoglobin are examples of hemeprotein that are essential in the storing and transports of oxygen in mammals. Hemoglobin is a quaternary protein that occurs in the red blood cell, whereas, myoglobin is a tertiary protein found the muscle cells of mammals. Althought they might differ in location and size, their function are similar. Being hemeproteins, they both contain a prosthetic group.His-F8 of the myoglobin, also known as the proximal histadine is covalently bonded to the 5th coordination position of the iron. And as an Oxygen binds to the 6th coordination position of the iron, a distal histidine(a histidine that doesn't bond directly with the Iron), His-E7 of the myoglobin binds to the Oxygen that is now covalently bonded to the iron. The same occurs for the hemoglobin, however, being a protein with 4 subunits, the hemoglobin contains 4 heme, therefore, allowing 4 Oxygen atoms to bind to the heme.