Jonathan Winger - Dissociation of nitric oxide from soluble guanylate cyclase and heme-nitric oxide/oxygen binding domain constructs

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      JOURNAL OF BIOLOGICAL CHEMISTRY Volume: 282 Issue: 2 Pages:   897-907 Published: JAN 12 2007


      Regulation of soluble guanylate cyclase (sGC), the primary NO   receptor, is linked to NO binding to the prosthetic heme group.   Recent studies have demonstrated that the degree and duration of   sGC activation depend on the presence and ratio of purine   nucleotides and on the presence of excess NO. We measured NO   dissociation from full-length alpha 1 beta 1 sGC, and the   constructs beta 1(1-194), beta 1(1-385), and beta 2(1-217), at 37   and 10 degrees C with and without the substrate analogue   guanosine-5'-[(alpha, beta-methylene] triphosphate (GMPCPP) or   the activator 3-(5'-hydroxymethyl-3'-furyl)-1-benzylindazole   (YC-1). NO dissociation from each construct was complex,   requiring two exponentials to fit the data. Decreasing the   temperature decreased the contribution of the faster exponential   for all constructs. Inclusion of YC-1 moderately accelerated NO   dissociation from sGC and beta 2(1-217) at 37 degrees C and   dramatically accelerated NO dissociation from sGC at 10 degrees   C. The presence of GMPCPP also dramatically accelerated NO   dissociation from sGC at 10 degrees C. This acceleration is due   to increases in the observed rate for each exponential and in the   contribution of the faster exponential. Increases in the   contribution of the faster exponential correlated with higher   activation of sGC by NO. These data indicate that the sGC   ferrous-nitrosyl complex adopts two 5-coordinate conformations, a   lower activity "closed" form, which releases NO slowly, and a   higher activity "open" form, which releases NO rapidly. The ratio   of these two species affects the overall rate of NO dissociation.   These results have implications for the function of sGC in vivo,   where there is evidence for two NO-regulated activity states.

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