2fsv
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Structure of transhydrogenase (dI.D135N.NAD+)2(dIII.E155W.NADP+)1 asymmetric complex
OverviewOverview
Transhydrogenase couples proton translocation across a membrane to hydride, transfer between NADH and NADP+. Previous x-ray structures of complexes of, the nucleotide-binding components of transhydrogenase ("dI2dIII1", complexes) indicate that the dihydronicotinamide ring of NADH can move, from a distal position relative to the nicotinamide ring of NADP+ to a, proximal position. The movement might be responsible for gating hydride, transfer during proton translocation. We have mutated three invariant, amino acids, Arg-127, Asp-135, and Ser-138, in the NAD(H)-binding site of, Rhodospirillum rubrum transhydrogenase. In each mutant, turnover by the, intact enzyme is strongly inhibited. Stopped-flow experiments using, dI2dIII1 complexes show that inhibition results from a block in the steps, associated with hydride transfer. Mutation of Asp-135 and Ser-138 had no, effect on the binding affinity of either NAD+ or NADH, but mutation of, Arg-127 led to much weaker binding of NADH and slightly weaker binding of, NAD+. X-ray structures of dI2dIII1 complexes carrying the mutations showed, that their effects were restricted to the locality of the bound NAD(H)., The results are consistent with the suggestion that in wild-type protein, movement of the Arg-127 side chain, and its hydrogen bonding to Asp-135, and Ser-138, stabilizes the dihydronicotinamide of NADH in the proximal, position for hydride transfer.
About this StructureAbout this Structure
2FSV is a Protein complex structure of sequences from Rhodospirillum rubrum with NAD, NAP and GOL as ligands. Active as Oxidoreductase, with EC number 1.6.1.2. Full crystallographic information is available from OCA.
ReferenceReference
The role of invariant amino acid residues at the hydride transfer site of proton-translocating transhydrogenase., Brondijk TH, van Boxel GI, Mather OC, Quirk PG, White SA, Jackson JB, J Biol Chem. 2006 May 12;281(19):13345-54. Epub 2006 Mar 13. PMID:16533815
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