1x14
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Crystal structure of E. coli transhydrogenase domain I with bound NAD
OverviewOverview
The dimeric integral membrane protein nicotinamide nucleotide, transhydrogenase is required for cellular regeneration of NADPH in, mitochondria and prokaryotes, for detoxification and biosynthesis, purposes. Under physiological conditions, transhydrogenase couples the, reversible reduction of NADP+ by NADH to an inward proton translocation, across the membrane. Here, we present crystal structures of the, NAD(H)-binding domain I of transhydrogenase from Escherichia coli, in the, absence as well as in the presence of oxidized and reduced substrate. The, structures were determined at 1.9-2.0 A resolution. Overall, the, structures are highly similar to the crystal structure of a previously, published NAD(H)-binding domain, from Rhodospirillum rubrum, transhydrogenase. However, this particular domain is unique, since it is, covalently connected to the integral-membrane part of transhydrogenase., Comparative studies between the structures of the two species reveal, extensively differing surface properties and point to the possible, importance of a rigid peptide (PAPP) in the connecting linker for, conformational coupling. Further, the kinetic analysis of a deletion, mutant, from which the protruding beta-hairpin was removed, indicates that, this structural element is important for catalytic activity, but not for, domain I:domain III interaction or dimer formation. Taken together, these, results have important implications for the enzyme mechanism of the large, group of transhydrogenases, including mammalian enzymes, which contain a, connecting linker between domains I and II.
About this StructureAbout this Structure
1X14 is a Single protein structure of sequence from Escherichia coli with NAD as ligand. Active as NAD(P)(+) transhydrogenase (AB-specific), with EC number 1.6.1.2 Full crystallographic information is available from OCA.
ReferenceReference
X-ray structure of domain I of the proton-pumping membrane protein transhydrogenase from Escherichia coli., Johansson T, Oswald C, Pedersen A, Tornroth S, Okvist M, Karlsson BG, Rydstrom J, Krengel U, J Mol Biol. 2005 Sep 16;352(2):299-312. PMID:16083909
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