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2fec

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{{STRUCTURE_2fec| PDB=2fec | SCENE= }}
{{STRUCTURE_2fec| PDB=2fec | SCENE= }}
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'''Structure of the E203Q mutant of the Cl-/H+ exchanger CLC-ec1 from E.Coli'''
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===Structure of the E203Q mutant of the Cl-/H+ exchanger CLC-ec1 from E.Coli===
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==Overview==
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CLC-ec1 is a prokaryotic CLC-type Cl(-)/H+ exchange transporter. Little is known about the mechanism of H+ coupling to Cl-. A critical glutamate residue, E148, was previously shown to be required for Cl(-)/H+ exchange by mediating proton transfer between the protein and the extracellular solution. To test whether an analogous H+ acceptor exists near the intracellular side of the protein, we performed a mutagenesis scan of inward-facing carboxyl-bearing residues and identified E203 as the unique residue whose neutralization abolishes H+ coupling to Cl- transport. Glutamate at this position is strictly conserved in all known CLCs of the transporter subclass, while valine is always found here in CLC channels. The x-ray crystal structure of the E203Q mutant is similar to that of the wild-type protein. Cl- transport rate in E203Q is inhibited at neutral pH, and the double mutant, E148A/E203Q, shows maximal Cl- transport, independent of pH, as does the single mutant E148A. The results argue that substrate exchange by CLC-ec1 involves two separate but partially overlapping permeation pathways, one for Cl- and one for H+. These pathways are congruent from the protein's extracellular surface to E148, and they diverge beyond this point toward the intracellular side. This picture demands a transport mechanism fundamentally different from familiar alternating-access schemes.
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(as it appears on PubMed at http://www.pubmed.gov), where 16316975 is the PubMed ID number.
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{{ABSTRACT_PUBMED_16316975}}
==About this Structure==
==About this Structure==
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[[Category: Clc-ec1]]
[[Category: Clc-ec1]]
[[Category: Clca_ecoli]]
[[Category: Clca_ecoli]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun May 4 03:47:53 2008''
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun Jul 27 16:53:02 2008''

Revision as of 13:53, 27 July 2008

Image:2fec.png

Template:STRUCTURE 2fec

Structure of the E203Q mutant of the Cl-/H+ exchanger CLC-ec1 from E.Coli

Template:ABSTRACT PUBMED 16316975

About this Structure

2FEC is a Single protein structure of sequence from Escherichia coli and Homo sapiens. Full crystallographic information is available from OCA.

Reference

Separate ion pathways in a Cl-/H+ exchanger., Accardi A, Walden M, Nguitragool W, Jayaram H, Williams C, Miller C, J Gen Physiol. 2005 Dec;126(6):563-70. PMID:16316975

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