Characterization of key residues in the subdomain encoded by exons 8 and 9 of human inducible nitric oxide synthase: a critical role for Asp-280 in substrate binding and subunit interactions
dc.contributor.author | Rashid, Bazlur | |
dc.date.accessioned | 2020-09-11T18:45:52Z | |
dc.date.available | 2020-09-11T18:45:52Z | |
dc.date.issued | 2001-08-28 | |
dc.description.abstract | Human inducible nitric oxide synthase (iNOS) is active as a dimer of two identical subunits. Each subunit has an amino-terminal oxygenase domain that binds the substrate l-Arg and the cofactors heme and tetrahydrobiopterin and a carboxyl-terminal reductase domain that binds FMN, FAD, and NADPH. We previously demonstrated that a subdomain in the oxygenase domain encoded by exons 8 and 9 is important for dimer formation and NO synthesis. Further, we identified Trp-260, Asn-261, Tyr-267, and Asp-280 as key residues in that subdomain. In this study, using an Escherichia coli expression system, we produced, purified, and characterized wild-type iNOS and iNOS-Ala mutants. Using H2O2-supported oxidation of Nω-hydroxy-l-Arg, we demonstrate that the iNOS mutants' inabilities to synthesize NO are due to selective defects in the oxygenase domain activity. Detailed characterization of the Asp-280–Ala mutant revealed that it retains a functional reductase domain, as measured by its ability to reduce cytochrome c. Gel permeation chromatography confirmed that the Asp-280–Ala mutant exists as a dimer, but, in contrast to wild-type iNOS, urea-generated monomers of the mutant fail to reassociate into dimers when incubated with l-Arg and tetrahydrobiopterin, suggesting inadequate subunit interaction. Spectral analysis reveals that the Asp-280–Ala mutant does not bind l-Arg. This indicates that, in addition to dimerization, proper subunit interaction is required for substrate binding. These data, by defining a critical role for Asp-280 in substrate binding and subunit interactions, give insights into the mechanisms of regulation of iNOS activity. | en_US |
dc.identifier.citation | Ghosh DK, Rashid MB, Crane B, Taskar V, Mast M, Misukonis MA, Weinberg JB, Eissa NT, 2001. Characterization of key residues in the subdomain encoded by exons 8 and 9 of human inducible nitric oxide synthase: a critical role for Asp-280 in substrate binding and subunit interactions. Proc Natl Acad Sci U S A. Aug 28; 98(18): 10392-7 | en_US |
dc.identifier.uri | https://hdl.handle.net/10657.1/2475 | |
dc.language.iso | en_US | en_US |
dc.publisher | Proc Natl Acad Sci U S A | en_US |
dc.title | Characterization of key residues in the subdomain encoded by exons 8 and 9 of human inducible nitric oxide synthase: a critical role for Asp-280 in substrate binding and subunit interactions | en_US |
dc.type | Article | en_US |
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