2flq
From Proteopedia
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Crystal Structure of Nitric Oxide Synthase from Geobacillus Stearothermophilus (ATCC 12980) complexed with L-arginine
Overview
In an effort to generate more stable reaction intermediates involved in, substrate oxidation by nitric-oxide synthases (NOSs), we have cloned, expressed, and characterized a thermostable NOS homolog from the, thermophilic bacterium Geobacillus stearothermophilus (gsNOS). As, expected, gsNOS forms nitric oxide (NO) from l-arginine via the stable, intermediate N-hydroxy l-arginine (NOHA). The addition of oxygen to, ferrous gsNOS results in long-lived heme-oxy complexes in the presence, (Soret peak 427 nm) and absence (Soret peak 413 nm) of substrates, l-arginine and NOHA. The substrate-induced red shift correlates with, hydrogen bonding between substrate and heme-bound oxygen resulting in, conversion to a ferric heme-superoxy species. In single turnover, experiments with NOHA, NO forms only in the presence of H(4)B. The crystal, structure of gsNOS at 3.2 AA of resolution reveals great similarity to, other known bacterial NOS structures, with the exception of differences in, the distal heme pocket, close to the oxygen binding site. In particular, a, Lys-356 (Bacillus subtilis NOS) to Arg-365 (gsNOS) substitution alters the, conformation of a conserved Asp carboxylate, resulting in movement of an, Ile residue toward the heme. Thus, a more constrained heme pocket may slow, ligand dissociation and increase the lifetime of heme-bound oxygen to, seconds at 4 degrees C. Similarly, the ferric-heme NO complex is also, stabilized in gsNOS. The slow kinetics of gsNOS offer promise for studying, downstream intermediates involved in substrate oxidation.
About this Structure
2FLQ is a Protein complex structure of sequences from Geobacillus stearothermophilus with and as ligands. Active as Nitric-oxide synthase, with EC number 1.14.13.39 Full crystallographic information is available from OCA.
Reference
Structure and reactivity of a thermostable prokaryotic nitric-oxide synthase that forms a long-lived oxy-heme complex., Sudhamsu J, Crane BR, J Biol Chem. 2006 Apr 7;281(14):9623-32. Epub 2006 Jan 11. PMID:16407211
Page seeded by OCA on Tue Jan 29 19:39:34 2008
