1NM5

R. rubrum transhydrogenase (dI.Q132N)2(dIII)1 asymmetric complex

Summary for 1NM5

• Entry DOI: 10.2210/pdb1nm5/pdb
• Related: 1HZZ
• Descriptor: NAD(P) transhydrogenase subunit alpha part 1, NAD(P) transhydrogenase subunit beta, NICOTINAMIDE-ADENINE-DINUCLEOTIDE, ... (6 entities in total)
• Functional Keywords: asymmetric complex, rossman domain, oxidoreductase
• Biological source: Rhodospirillum rubrum; More
• Cellular location: Cell inner membrane; Multi-pass membrane protein (By similarity): Q59765
• Total number of polymer chains: 3
• Total formula weight: 104269.38

Authors

Van Boxel, G.I.,Quirk, P.G.,Cotton, N.P.,White, S.A.,Jackson, J.B. (deposition date: 2003-01-09, release date: 2004-01-13, Last modification date: 2023-08-16)

Primary citation

van Boxel, G.I.,Quirk, P.G.,Cotton, N.P.,White, S.A.,Jackson, J.B.
Glutamine 132 in the NAD(H)-binding component of proton-translocating transhydrogenase tethers the nucleotides before hydride transfer.
Biochemistry, 42:1217-1226, 2003

PubMed Abstract: Transhydrogenase, found in bacterial membranes and inner mitochondrial membranes of animal cells, couples the redox reaction between NAD(H) and NADP(H) to proton translocation. In this work, the invariant Gln132 in the NAD(H)-binding component (dI) of the Rhodospirillum rubrum transhydrogenase was substituted with Asn (to give dI.Q132N). Mixtures of the mutant protein and the NADP(H)-binding component (dIII) of the enzyme readily produced an asymmetric complex, (dI.Q132N)(2)dIII(1). The X-ray structure of the complex revealed specific changes in the interaction between bound nicotinamide nucleotides and the protein at the hydride transfer site. The first-order rate constant of the redox reaction between nucleotides bound to (dI.Q132N)(2)dIII(1) was <1% of that for the wild-type complex, and the deuterium isotope effect was significantly decreased. The nucleotide binding properties of the dI component in the complex were asymmetrically affected by the Gln-to-Asn mutation. In intact, membrane-bound transhydrogenase, the substitution completely abolished all catalytic activity. The results suggest that Gln132 in the wild-type enzyme behaves as a "tether" or a "tie" in the mutual positioning of the (dihydro)nicotinamide rings of NAD(H) and NADP(H) for hydride transfer during the conformational changes that are coupled to the translocation of protons across the membrane. This ensures that hydride transfer is properly gated and does not take place in the absence of proton translocation.

PubMed: 12564924
DOI: 10.1021/bi027032e

Experimental method

X-RAY DIFFRACTION (2.4 Å)