Abstract
Nitric oxide reductase cytochrome P450nor catalyzes an unusual reaction, direct electron transfer from NAD(P)H to bound heme. Here, we succeeded in determining the crystal structure of P450nor in a complex with an NADH analogue, nicotinic acid adenine dinucleotide, which provides conclusive evidence for the mechanism of the unprecedented electron transfer. Comparison of the structure with those of dinucleotide-free forms revealed a global conformational change accompanied by intriguing local movements caused by the binding of the pyridine nucleotide. Arg64 and Arg174 fix the pyrophosphate moiety upon the dinucleotide binding. Stereo-selective hydride transfer from NADH to NO-bound heme was suggested from the structure, the nicotinic acid ring being fixed near the heme by the conserved Thr residue in the I-helix and the upward-shifted propionate side-chain of the heme. A proton channel near the NADH channel is formed upon the dinucleotide binding, which should direct continuous transfer of the hydride and proton. A salt-bridge network (Glu71-Arg64-Asp88) was shown to be crucial for a high catalytic turnover.
Original language | English (US) |
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Pages (from-to) | 207-217 |
Number of pages | 11 |
Journal | Journal of Molecular Biology |
Volume | 342 |
Issue number | 1 |
DOIs | |
State | Published - Sep 3 2004 |
Externally published | Yes |
Keywords
- cytochrome P450nor
- denitrification
- hydride transfer
- NADH-binding
- proton channel
ASJC Scopus subject areas
- Biophysics
- Structural Biology
- Molecular Biology