3HSN: Ternary Structure Of Neuronal Nitric Oxide Synthase With Nha And Co Bound

Citation:
Abstract
The X-ray structures of neuronal nitric oxide synthase (nNOS) with N(omega)-hydroxy-l-arginine (l-NHA) and CO (or NO) bound have been determined at 1.91-2.2 A resolution. Microspectrophotometric techniques confirmed reduced redox state and the status of diatomic ligand complexes during X-ray diffraction data collection. The structure of nNOS-NHA-NO, a close mimic to the dioxygen complex, provides a picture of the potential interactions between the heme-bound diatomic ligand, substrate l-NHA, and the surrounding protein and solvent structure environment. The OH group of l-NHA in the X-ray structures deviates from the plane of the guanidinium moiety substantially, indicating that the OH-bearing, protonated guanidine N(omega) nitrogen of l-NHA has substantial sp(3) hybridization character. This nitrogen geometry, different from that of the guanidinium N(omega) nitrogen of l-arginine, allows a hydrogen bond to be donated to the proximal oxygen of the heme-bound dioxygen complex, thus preventing cleavage of the O-O bond. Instead, it favors the stabilization of the ferric-hydroperoxy intermediate, Fe(3+)-OOH(-), which serves as the active oxidant in the conversion of l-NHA to NO and citrulline in the second reaction of the NOS.
PDB ID: 3HSNDownload
MMDB ID: 77520
PDB Deposition Date: 2009/6/10
Updated in MMDB: 2009/11
Experimental Method:
x-ray diffraction
Resolution: 1.91  Å
Source Organism:
Similar Structures:
Biological Unit for 3HSN: dimeric; determined by author and by software (PISA)
Molecular Components in 3HSN
Label Count Molecule
Proteins (2 molecules)
2
Nitric Oxide Synthase, Brain(Gene symbol: Nos1)
Molecule annotation
Chemicals (18 molecules)
1
2
2
2
3
2
4
2
5
2
6
1
7
7
* Click molecule labels to explore molecular sequence information.

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