Urea transporter
Encyclopedia
An urea transporter is a membrane transport protein, transporting urea
. Humans and other mammals have two types of urea transport proteins, UT-A and UT-B. The UT-A proteins are important for renal urea handling
and are produced by alternative splicing of the SLC14A2
gene. Urea transport in the kidney is regulated by vasopressin
.
The structure of a urea transport family protein from Desulfovibrio vulgaris
was determined by x-ray crystallography
. The structure has a pathway through the membrane that is similar to that of ion channel
proteins, accounting for the ability of urea transport proteins to move up to one million urea molecules per second across the membrane.
s: UT-A (SLC14A2
) and UT-B (SLC14A1
). Multiple protein isoform
s derived from each gene are produced by alternative splicing
and alternative promotors.
Urea transporter A1 transports urea across the apical membrane into the intracellular space of luminal cells in the inner medullary collecting duct of the kidneys. UT-1 is activated by ADH
, but is a passive transporter. It reabsorbs up to 40% of the original filtered load of urea.
Urea Transporter 2 transports urea across the apical membrane into the luminal space of cells in the thin descending loop of Henle of the kidneys.
Urea transporter 3 transports urea into the interstitium of the Inner Medullary Collecting Duct.
, intestine
, and at the blood–brain barrier. The SLC14A1
gene codes for the UT-B protein. UT-B is expressed at the basolateral and apical regions of the descending Vasa recta
.
Urea
Urea or carbamide is an organic compound with the chemical formula CO2. The molecule has two —NH2 groups joined by a carbonyl functional group....
. Humans and other mammals have two types of urea transport proteins, UT-A and UT-B. The UT-A proteins are important for renal urea handling
Renal urea handling
Renal urea handling is the part of renal physiology that deals with the reabsorption and secretion of urea. Movement of large amounts of urea across cell membranes is made possible by urea transporter proteins....
and are produced by alternative splicing of the SLC14A2
SLC14A2
Urea transporter, kidney also known as urea transporter 2 or solute carrier family 14 member 2 is a protein that in humans is encoded by the SLC14A2 gene.- Function :...
gene. Urea transport in the kidney is regulated by vasopressin
Vasopressin
Arginine vasopressin , also known as vasopressin, argipressin or antidiuretic hormone , is a neurohypophysial hormone found in most mammals, including humans. Vasopressin is a peptide hormone that controls the reabsorption of molecules in the tubules of the kidneys by affecting the tissue's...
.
The structure of a urea transport family protein from Desulfovibrio vulgaris
Desulfovibrio vulgaris
Desulfovibrio vulgaris is a species of Gram-negative sulfate-reducing bacteria in the Desulfovibrionaceae family....
was determined by x-ray crystallography
X-ray crystallography
X-ray crystallography is a method of determining the arrangement of atoms within a crystal, in which a beam of X-rays strikes a crystal and causes the beam of light to spread into many specific directions. From the angles and intensities of these diffracted beams, a crystallographer can produce a...
. The structure has a pathway through the membrane that is similar to that of ion channel
Ion channel
Ion channels are pore-forming proteins that help establish and control the small voltage gradient across the plasma membrane of cells by allowing the flow of ions down their electrochemical gradient. They are present in the membranes that surround all biological cells...
proteins, accounting for the ability of urea transport proteins to move up to one million urea molecules per second across the membrane.
Types
In mammals, there are two urea transporter geneGene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
s: UT-A (SLC14A2
SLC14A2
Urea transporter, kidney also known as urea transporter 2 or solute carrier family 14 member 2 is a protein that in humans is encoded by the SLC14A2 gene.- Function :...
) and UT-B (SLC14A1
SLC14A1
Urea transporter, erythrocyte is a protein that in humans is encoded by the SLC14A1 gene.-Function:The SLC14A1 codes for a urea transporter that is expressed in erythrocytes and kidney. SLC14A2 and SLC14A1 constitute solute carrier family 14. UTB proteins constitute the Kidd antigen...
). Multiple protein isoform
Protein isoform
A protein isoform is any of several different forms of the same protein. Different forms of a protein may be produced from related genes, or may arise from the same gene by alternative splicing. A large number of isoforms are caused by single-nucleotide polymorphisms or SNPs, small genetic...
s derived from each gene are produced by alternative splicing
Alternative splicing
Alternative splicing is a process by which the exons of the RNA produced by transcription of a gene are reconnected in multiple ways during RNA splicing...
and alternative promotors.
UT-A1
Urea transporter A1 transports urea across the apical membrane into the intracellular space of luminal cells in the inner medullary collecting duct of the kidneys. UT-1 is activated by ADH
Vasopressin
Arginine vasopressin , also known as vasopressin, argipressin or antidiuretic hormone , is a neurohypophysial hormone found in most mammals, including humans. Vasopressin is a peptide hormone that controls the reabsorption of molecules in the tubules of the kidneys by affecting the tissue's...
, but is a passive transporter. It reabsorbs up to 40% of the original filtered load of urea.
UT-A2
Urea Transporter 2 transports urea across the apical membrane into the luminal space of cells in the thin descending loop of Henle of the kidneys.
UT-A3
Urea transporter 3 transports urea into the interstitium of the Inner Medullary Collecting Duct.
UT-B
UT-B is widely expressed and has been studied in erythrocytes, kidneyKidney
The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...
, intestine
Intestine
In human anatomy, the intestine is the segment of the alimentary canal extending from the pyloric sphincter of the stomach to the anus and, in humans and other mammals, consists of two segments, the small intestine and the large intestine...
, and at the blood–brain barrier. The SLC14A1
SLC14A1
Urea transporter, erythrocyte is a protein that in humans is encoded by the SLC14A1 gene.-Function:The SLC14A1 codes for a urea transporter that is expressed in erythrocytes and kidney. SLC14A2 and SLC14A1 constitute solute carrier family 14. UTB proteins constitute the Kidd antigen...
gene codes for the UT-B protein. UT-B is expressed at the basolateral and apical regions of the descending Vasa recta
Vasa recta
In the blood supply of the kidney, the vasa recta renis form a series of straight capillaries in the medulla...
.