Heme‐nitric oxide/oxygen binding (H‐NOX) domains bind gaseous ligands for signal transduction in organisms spanning prokaryotic and eukaryotic kingdoms. In the bioluminescent marine bacterium
The crystal structure of the NADH:quinone oxidoreductase PA1024 has been solved in complex with NAD+to 2.2 Å resolution. The nicotinamide C4 is 3.6 Å from the FMN N5 atom, with a suitable orientation for facile hydride transfer. NAD+binds in a folded conformation at the interface of the TIM‐barrel domain and the extended domain of the enzyme. Comparison of the enzyme‐NAD+structure with that of the ligand‐free enzyme revealed a different conformation of a short loop (75–86) that is part of the NAD+‐binding pocket. P78, P82, and P84 provide internal rigidity to the loop, whereas Q80 serves as an active site latch that secures the NAD+within the binding pocket. An interrupted helix consisting of two α‐helices connected by a small three‐residue loop binds the pyrophosphate moiety of NAD+. The adenine moiety of NAD+appears to π–π stack with Y261. Steric constraints between the adenosine ribose of NAD+, P78, and Q80, control the strict specificity of the enzyme for NADH. Charged residues do not play a role in the specificity of PA1024 for the NADH substrate.
more » « less- PAR ID:
- 10078611
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Protein Science
- Volume:
- 28
- Issue:
- 1
- ISSN:
- 0961-8368
- Page Range / eLocation ID:
- p. 167-175
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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