| 词条 | Urea transporter |
| 释义 |
| Symbol = UT | Name = UT | image = | width = | caption = crystal structure of the urea transporter from desulfovibrio vulgaris bound to 1,3-dimethylurea | Pfam = PF03253 | Pfam_clan = | InterPro = IPR004937 | SMART = | PROSITE = | MEROPS = | SCOP = | TCDB = 1.A.28 | OPM family = 13 | OPM protein = 3k3f | CAZy = | CDD = }} A 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.[1] Urea transport in the kidney is regulated by vasopressin.[2] The structure of a urea transport family protein from Desulfovibrio vulgaris was determined by x-ray crystallography.[3] 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. Urea transporters can be inhibited by the action of urea analogues like thiourea and glycosides like phloretin.[4] Their inhibition results in diuresis due to urea induced osmosis in the collecting ducts of the kidney.[5] TypesIn mammals, there are two urea transporter genes: UT-A (SLC14A2) and UT-B (SLC14A1). Multiple protein isoforms derived from each gene are produced by alternative splicing and alternative promotors.[5] === 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, but is a passive transporter. It reabsorbs up to 70% of the original filtered load of urea.[5] === 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.[5] === UT-A3 === Urea transporter 3 transports urea into the interstitium of the Inner Medullary Collecting Duct.[6] === UT-A4 === Urea transporter 4 has been detected in rat but not mouse kidney medulla.[6] UT-A5Urea transporter 5 is not expressed in the kidney but in the testis.[6] UT-BUT-B is widely expressed and has been studied in erythrocytes,[7] kidney, intestine,[8] and at the blood–brain barrier.[9] The SLC14A1 gene codes for the UT-B protein. UT-B is expressed at the basolateral and apical regions of the descending Vasa recta.[5] References1. ^{{cite journal |vauthors=Maciver B, Smith CP, Hill WG, Zeidel ML | title = Functional characterization of mouse urea transporters UT-A2 and UT-A3 expressed in purified Xenopus laevis oocyte plasma membranes | journal = Am. J. Physiol. Renal Physiol. | volume = 294 | issue = 4 | pages = F956–64 |date=April 2008 | pmid = 18256317 | doi = 10.1152/ajprenal.00229.2007 }} {{Membrane transport proteins|bg|bg1}}2. ^{{cite journal |vauthors=Sands JM, Blount MA, Klein JD | title = Regulation of renal urea transport by vasopressin | journal = Trans. Am. Clin. Climatol. Assoc. | volume = 122 | issue = | pages = 82–92 | year = 2011 | pmid = 21686211 | pmc = 3116377 | doi = }} 3. ^{{cite journal |vauthors=Levin EJ, Quick M, Zhou M | title = Crystal structure of a bacterial homologue of the kidney urea transporter | journal = Nature | volume = 462 | issue = 7274 | pages = 757–61 |date=December 2009 | pmid = 19865084 | pmc = 2871279 | doi = 10.1038/nature08558 }} 4. ^{{cite journal |vauthors=Chou CL, Knepper MA | title = Inhibition of urea transport in inner medullary collecting duct by phloretin and urea analogues | journal = Am. J. Physiol. | volume = 257 | issue = 3 Pt 2 | pages = F359–65 |date=September 1989 | pmid = 2506765 | doi = }} 5. ^1 2 3 4 {{cite journal |vauthors=Fenton RA, Knepper MA | title = Urea and renal function in the 21st century: insights from knockout mice | journal = J. Am. Soc. Nephrol. | volume = 18 | issue = 3 | pages = 679–88 |date=March 2007 | pmid = 17251384 | doi = 10.1681/ASN.2006101108 }} 6. ^1 2 {{cite journal | title = Urea transporter UT-A | journal = UCSD Nature Molecule Pages | year = 2005 | doi = 10.1038/mp.a002589.01 | author = Fenton RA | volume = 18 | pages = 679 }} 7. ^{{cite journal |vauthors=Yang B, Verkman AS | title = Analysis of double knockout mice lacking aquaporin-1 and urea transporter UT-B. Evidence for UT-B-facilitated water transport in erythrocytes | journal = J. Biol. Chem. | volume = 277 | issue = 39 | pages = 36782–6 |date=September 2002 | pmid = 12133842 | doi = 10.1074/jbc.M206948200 }} 8. ^{{cite journal |vauthors=Collins D, Winter DC, Hogan AM, Schirmer L, Baird AW, Stewart GS | title = Differential protein abundance and function of UT-B urea transporters in human colon | journal = Am. J. Physiol. Gastrointest. Liver Physiol. | volume = 298 | issue = 3 | pages = G345–51 |date=March 2010 | pmid = 19926813 | doi = 10.1152/ajpgi.00405.2009 | pmc = 3774180 }} 9. ^{{cite journal |vauthors=Dahlin A, Royall J, Hohmann JG, Wang J | title = Expression profiling of the solute carrier gene family in the mouse brain | journal = J. Pharmacol. Exp. Ther. | volume = 329 | issue = 2 | pages = 558–70 |date=May 2009 | pmid = 19179540 | pmc = 2672879 | doi = 10.1124/jpet.108.149831 }} 2 : Transmembrane transporters|Renal physiology |
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