2bs4

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{{STRUCTURE_2bs4| PDB=2bs4 | SCENE= }}
{{STRUCTURE_2bs4| PDB=2bs4 | SCENE= }}
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'''GLU C180-> ILE VARIANT QUINOL:FUMARATE REDUCTASE FROM WOLINELLA SUCCINOGENES'''
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===GLU C180-> ILE VARIANT QUINOL:FUMARATE REDUCTASE FROM WOLINELLA SUCCINOGENES===
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==Overview==
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Reconciliation of apparently contradictory experimental results obtained on the quinol:fumarate reductase, a diheme-containing respiratory membrane protein complex from Wolinella succinogenes, was previously obtained by the proposal of the so-called "E pathway hypothesis." According to this hypothesis, transmembrane electron transfer via the heme groups is strictly coupled to cotransfer of protons via a transiently established pathway thought to contain the side chain of residue Glu-C180 as the most prominent component. Here we demonstrate that, after replacement of Glu-C180 with Gln or Ile by site-directed mutagenesis, the resulting mutants are unable to grow on fumarate, and the membrane-bound variant enzymes lack quinol oxidation activity. Upon solubilization, however, the purified enzymes display approximately 1/10 of the specific quinol oxidation activity of the wild-type enzyme and unchanged quinol Michaelis constants, K(m). The refined x-ray crystal structures at 2.19 A and 2.76 A resolution, respectively, rule out major structural changes to account for these experimental observations. Changes in the oxidation-reduction heme midpoint potential allow the conclusion that deprotonation of Glu-C180 in the wild-type enzyme facilitates the reoxidation of the reduced high-potential heme. Comparison of solvent isotope effects indicates that a rate-limiting proton transfer step in the wild-type enzyme is lost in the Glu-C180 --&gt; Gln variant. The results provide experimental evidence for the validity of the E pathway hypothesis and for a crucial functional role of Glu-C180.
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{{ABSTRACT_PUBMED_16380425}}
==About this Structure==
==About this Structure==
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[[Category: Transmembrane]]
[[Category: Transmembrane]]
[[Category: Tricarboxylic acid cycle]]
[[Category: Tricarboxylic acid cycle]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun Jul 27 13:28:37 2008''

Revision as of 10:28, 27 July 2008

Image:2bs4.png

Template:STRUCTURE 2bs4

GLU C180-> ILE VARIANT QUINOL:FUMARATE REDUCTASE FROM WOLINELLA SUCCINOGENES

Template:ABSTRACT PUBMED 16380425

About this Structure

2BS4 is a Protein complex structure of sequences from Wolinella succinogenes. Full crystallographic information is available from OCA.

Reference

Experimental support for the "E pathway hypothesis" of coupled transmembrane e- and H+ transfer in dihemic quinol:fumarate reductase., Lancaster CR, Sauer US, Gross R, Haas AH, Graf J, Schwalbe H, Mantele W, Simon J, Madej MG, Proc Natl Acad Sci U S A. 2005 Dec 27;102(52):18860-5. PMID:16380425

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