“Bicarbonate transporter protein”的意思、由来-开放百科全书

In molecular biology, bicarbonate transporter proteins are proteins which transport bicarbonate. Bicarbonate (HCO₃ ⁻) transport mechanisms are the principal regulators of pH in animal cells. Such transport also plays a vital role in acid-base movements in the stomach, pancreas, intestine, kidney, reproductive organs and the central nervous system. Functional studies have suggested four different HCO₃ ⁻ transport modes. Anion exchanger proteins exchange HCO₃ ⁻ for Cl⁻ in a reversible, electroneutral manner.^[1] Na⁺/HCO₃ ⁻ co-transport proteins mediate the coupled movement of Na⁺ and HCO₃ ⁻ across plasma membranes, often in an electrogenic manner.^[2] Na⁺ driven Cl⁻/HCO₃ ⁻ exchange and K⁺/HCO₃ ⁻ exchange activities have also been detected in certain cell types, although the molecular identities of the proteins responsible remain to be determined.

Sequence analysis of the two families of HCO₃ ⁻ transporters that have been cloned to date (the anion exchangers and Na⁺/HCO₃ ⁻ co-transporters) reveals that they are homologous. This is not entirely unexpected, given that they both transport HCO₃ ⁻ and are inhibited by a class of pharmacological agents called disulphonic stilbenes.^[3] They share around ~25-30% sequence identity, which is distributed along their entire sequence length, and have similar predicted membrane topologies, suggesting they have ~10 transmembrane (TM) domains.

A conserved domain is found at the C terminus of many bicarbonate transport proteins. It is also found in some plant proteins responsible for boron transport.^[4] In these proteins it covers almost the entire length of the sequence.

The Band 3 anion exchange proteins that exchange bicarbonate are the most abundant polypeptide in the red blood cell membrane, comprising 25% of the total membrane protein. The cytoplasmic domain of band 3 functions primarily as an anchoring site for other membrane-associated proteins. Included among the protein ligands of this domain are ankyrin, protein 4.2, protein 4.1, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), phosphofructokinase, aldolase, hemoglobin, hemichromes, and the protein tyrosine kinase (p72syk).^[5]

References

1. ^{{cite journal | author = Kopito RR | title = Molecular biology of the anion exchanger gene family | journal = Int. Rev. Cytol. | volume = 123 | issue = | pages = 177–99 | year = 1990 | pmid = 2289848 | doi = 10.1016/S0074-7696(08)60674-9| url = }}
2. ^{{cite journal |vauthors=Boron WF, Fong P, Hediger MA, Boulpaep EL, Romero MF | title = The electrogenic Na/HCO3 cotransporter | journal = Wien. Klin. Wochenschr. | volume = 109 | issue = 12-13 | pages = 445–56 |date=June 1997 | pmid = 9261985 | doi = | url = }}
3. ^{{cite journal |vauthors=Burnham CE, Amlal H, Wang Z, Shull GE, Soleimani M | title = Cloning and functional expression of a human kidney Na+:HCO3- cotransporter | journal = J. Biol. Chem. | volume = 272 | issue = 31 | pages = 19111–4 |date=August 1997 | pmid = 9235899 | doi = 10.1074/jbc.272.31.19111| url = }}
4. ^{{cite journal |vauthors=Takano J, Noguchi K, Yasumori M, Kobayashi M, Gajdos Z, Miwa K, Hayashi H, Yoneyama T, Fujiwara T | title = Arabidopsis boron transporter for xylem loading | journal = Nature | volume = 420 | issue = 6913 | pages = 337–40 |date=November 2002 | pmid = 12447444 | doi = 10.1038/nature01139 | url = }}
5. ^{{Cite journal | last1 = Zhang | first1 = D. | last2 = Kiyatkin | first2 = A. | last3 = Bolin | first3 = J. T. | last4 = Low | first4 = P. S. | title = Crystallographic structure and functional interpretation of the cytoplasmic domain of erythrocyte membrane band 3 | journal = Blood | volume = 96 | issue = 9 | pages = 2925–2933 | year = 2000 | pmid = 11049968}}