2bs3

File:2bs3.gif

spinqualitylabelsall models 2bs3, resolution 2.19Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

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

OverviewOverview

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 --> Gln variant. The results provide experimental evidence, for the validity of the E pathway hypothesis and for a crucial functional, role of Glu-C180.

About this StructureAbout this Structure

2BS3 is a Protein complex structure of sequences from Wolinella succinogenes with , , , , , , and as ligands. Active as Succinate dehydrogenase, with EC number 1.3.99.1 Known structural/functional Site: . Full crystallographic information is available from OCA.

ReferenceReference

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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