1jwk
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Murine Inducible Nitric Oxide Synthase Oxygenase Dimer (Delta 65) with W457A Mutation at Tetrahydrobiopterin Binding Site
OverviewOverview
To better understand potential roles of conserved Trp457 of the murine, inducible nitric oxide synthase oxygenase domain (iNOS(ox); residues, 1-498) in maintaining the structural integrity of the, (6R)-5,6,7,8-tetrahydrobiopterin (H(4)B) binding site located at the dimer, interface and in supporting H(4)B redox activity, we determined, crystallographic structures of W457F and W457A mutant iNOS(ox) dimers, (residues 66-498). In W457F iNOS(ox), all the important hydrogen-bonding, and aromatic stacking interactions that constitute the H(4)B binding site, and that bridge the H(4)B and heme sites are preserved. In contrast, the, W457A mutation results in rearrangement of the Arg193 side chain, orienting its terminal guanidinium group almost perpendicular to the ring, plane of H(4)B. Although Trp457 is not required for dimerization, both, Trp457 mutations led to the increased mobility of the N-terminal H(4)B, binding segment (Ser112-Met114), which might indicate reduced stability of, the Trp457 mutant dimers. The Trp457 mutant structures show decreased, pi-stacking with bound pterin when the wild-type pi-stacking Trp457, position is occupied with the smaller Phe457 in W457F or positive Arg193, in W457A. The reduced pterin pi-stacking in these mutant structures, relative to that in the wild-type, implies stabilization of reduced H(4)B, and destabilization of the pterin radical, consequently slowing electron, transfer to the heme ferrous-dioxy (Fe(II)O(2)) species during catalysis., These crystal structures therefore aid elucidation of the roles and, importance of conserved Trp457 in maintaining the structural integrity of, the H(4)B binding site and of H(4)B-bound dimers, and in influencing the, rate of electron transfer between H(4)B and heme in NOS catalysis.
About this StructureAbout this Structure
1JWK is a Single protein structure of sequence from Mus musculus with BOG, HEM, HBI, EDO and GOL as ligands. Active as Nitric-oxide synthase, with EC number 1.14.13.39 Full crystallographic information is available from OCA.
ReferenceReference
Structures of tetrahydrobiopterin binding-site mutants of inducible nitric oxide synthase oxygenase dimer and implicated roles of Trp457., Aoyagi M, Arvai AS, Ghosh S, Stuehr DJ, Tainer JA, Getzoff ED, Biochemistry. 2001 Oct 30;40(43):12826-32. PMID:11669619
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