2fec

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

spinqualitylabelsall models 2fec, resolution 3.97Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 2fec is a 6 chain structure with sequence from Escherichia coli and Homo sapiens. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Related: 1ots, 2fed, 2fee Gene: clcA, eriC (Escherichia coli) Resources: FirstGlance, OCA, RCSB, PDBsum Function [CLCA_ECOLI] Proton-coupled chloride transporter. Functions as antiport system and exchanges two chloride ions for 1 proton. Probably acts as an electrical shunt for an outwardly-directed proton pump that is linked to amino acid decarboxylation, as part of the extreme acid resistance (XAR) response. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMed 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. 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 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Monoclonal Antibody

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