Three-Dimensional Model for the Human Cl-/HCO3- Exchanger, AE1, by Homology to the E. coli ClC Protein

JOURNAL OF MOLECULAR BIOLOGY

卷:425

Article

Bonar, Pamela¹  Schneider, Hans-Peter²  Becker, Holger M.³  Deitmer, Joachim W.²  Casey, Joseph R.¹ 

[1] Univ Alberta, Dept Biochem, Membrane Prot Dis Res Grp, Edmonton, AB T6G 2H7, Canada

[2] Tech Univ Kaiserslautern, Fachbereich Biol, Abt Allgemeine Zool, D-67653 Kaiserslautern, Germany

[3] Tech Univ Kaiserslautern, Fachbereich Biol, Arbeitsgrp Zool Membrantransport, D-67653 Kaiserslautern, Germany

关键词: bicarbonate transporters;    homology model;    transport mechanism;    mutagenesis;   

DOI  :  10.1016/j.jmb.2013.04.005

来源: Elsevier

【 摘 要 】

AE1 mediates electroneutral 1:1 exchange of bicarbonate for chloride across the plasma membrane of erythrocytes and type A cells of the renal collecting duct. No high-resolution structure is available for the AE1 membrane domain, which alone is required for its transport activity. A recent electron microscopy structure of the AE1 membrane domain was proposed to have a similar protein fold to ClC chloride channels. We developed a three-dimensional homology model of the AE1 membrane domain, using the Escherichia coli ClC channel structure as a template. This model agrees well with a long list of biochemically established spatial constraints for AE1. To investigate the AE1 transport mechanism, we created point mutations in regions corresponding to E. coli ClC transport mechanism residues. When expressed in HEK293 cells, several mutants had Cl-/HCO3- exchange rates significantly different from that of wild-type AE1. When further assessed in Xenopus laevis oocytes, there were significant changes in the transport activity of several AE1 point mutants as assessed by changes in pH. None of the mutants, however, added an electrogenic component to AE1 transport activity. This indicates that the AE1 point mutants altered the transport activity of AE1, without changing its electrogenicity and stoichiometry. The homology model successfully identified residues in AE1 that are critical to AE1 transport activity. Thus, we conclude that AE1 has a similar protein fold to ClC chloride channels. (C) 2013 The Authors. Published by Elsevier Ltd. All rights reserved.

【 授权许可】

Free