2fec: Difference between revisions
New page: left|200px<br /><applet load="2fec" size="450" color="white" frame="true" align="right" spinBox="true" caption="2fec, resolution 3.967Å" /> '''Structure of the E2... |
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[[Image:2fec.gif|left|200px]]<br /><applet load="2fec" size=" | [[Image:2fec.gif|left|200px]]<br /><applet load="2fec" size="350" color="white" frame="true" align="right" spinBox="true" | ||
caption="2fec, resolution 3.967Å" /> | caption="2fec, resolution 3.967Å" /> | ||
'''Structure of the E203Q mutant of the Cl-/H+ exchanger CLC-ec1 from E.Coli'''<br /> | '''Structure of the E203Q mutant of the Cl-/H+ exchanger CLC-ec1 from E.Coli'''<br /> | ||
==Overview== | ==Overview== | ||
CLC-ec1 is a prokaryotic CLC-type Cl(-)/H+ exchange transporter. Little is | 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. | ||
==About this Structure== | ==About this Structure== | ||
2FEC is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli] and [http://en.wikipedia.org/wiki/Homo_sapiens Homo sapiens]. Full crystallographic information is available from [http:// | 2FEC is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli] and [http://en.wikipedia.org/wiki/Homo_sapiens Homo sapiens]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=2FEC OCA]. | ||
==Reference== | ==Reference== | ||
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[[Category: Miller, C.]] | [[Category: Miller, C.]] | ||
[[Category: Nguitragool, W.]] | [[Category: Nguitragool, W.]] | ||
[[Category: Walden, M | [[Category: Walden, M P.]] | ||
[[Category: Williams, C.]] | [[Category: Williams, C.]] | ||
[[Category: clc-ec1; clca_ecoli; chloride/proton exchange transporter]] | [[Category: clc-ec1; clca_ecoli; chloride/proton exchange transporter]] | ||
''Page seeded by [http:// | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 17:20:32 2008'' | ||
Revision as of 18:20, 21 February 2008
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Structure of the E203Q mutant of the Cl-/H+ exchanger CLC-ec1 from E.Coli
OverviewOverview
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.
About this StructureAbout this Structure
2FEC is a Single protein structure of sequence from Escherichia coli and Homo sapiens. Full crystallographic information is available from OCA.
ReferenceReference
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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