1l7d
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(New page: 200px<br /><applet load="1l7d" size="450" color="white" frame="true" align="right" spinBox="true" caption="1l7d, resolution 1.81Å" /> '''Crystal Structure of...)
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Revision as of 18:13, 20 November 2007
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Crystal Structure of R. rubrum Transhydrogenase Domain I without Bound NAD(H)
Overview
Transhydrogenase (TH) is a dimeric integral membrane enzyme in, mitochondria and prokaryotes that couples proton translocation across a, membrane with hydride transfer between NAD(H) and NADP(H) in soluble, domains. Crystal structures of the NAD(H) binding alpha1 subunit (domain, I) of Rhodospirillum rubrum TH have been determined at 1.8 A resolution in, the absence of dinucleotide and at 1.9 A resolution with NADH bound. Each, structure contains two domain I dimers in the asymmetric unit (AB and CD);, the dimers are intimately associated and related by noncrystallographic, 2-fold axes. NADH binds to subunits A and D, consistent with the, half-of-the-sites reactivity of the enzyme. The conformation of NADH in, subunits A and D is very similar; the nicotinamide is in the anti, conformation, the A-face is exposed to solvent, and both N7 and O7, participate in hydrogen bonds. Comparison of subunits A and D to six, independent copies of the subunit without bound NADH reveals multiple, conformations for residues and loops surrounding the NADH site, indicating, flexibility for binding and release of the substrate (product). The, NADH-bound structure is also compared to the structures of R. rubrum, domain I with NAD bound (PDB code 1F8G) and with NAD bound in complex with, domain III of TH (PDB code 1HZZ). The NADH- vs NAD-bound domain I, structures reveal conformational differences in conserved residues in the, NAD(H) binding site and in dinucleotide conformation that are correlated, with the net charge, i.e., oxidation state, of the nicotinamides. The, comparisons illustrate how nicotinamide oxidation state can affect the, domain I conformation, which is relevant to the hydride transfer step of, the overall reaction.
About this Structure
1L7D is a Single protein structure of sequence from Rhodospirillum rubrum. Active as NAD(P)(+) transhydrogenase (B-specific), with EC number 1.6.1.1 Full crystallographic information is available from OCA.
Reference
Crystal structures of transhydrogenase domain I with and without bound NADH., Prasad GS, Wahlberg M, Sridhar V, Sundaresan V, Yamaguchi M, Hatefi Y, Stout CD, Biochemistry. 2002 Oct 22;41(42):12745-54. PMID:12379117
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