Effect of solution viscosity on intraprotein electron transfer between the FMN and heme domains in inducible nitric oxide synthase

摘要

TheFMN–hemeintraproteinelectrontransfer(IET)kineticsinahumaninducibleNOS(iNOS)oxygenase/FMNconstructweredeterminedbylaserflashphotolysisasafunctionofsolutionviscosity(1.0–3.0cP).Inthepresenceofethyleneglycolorsucrose,anappreciabledecreaseintheIETrateconstantvaluewasobservedwithanincreaseinthesolutionviscosity.TheIETrateconstantisinverselyproportionaltotheviscosityforbothviscosogens.Thisdemonstratesthatviscosity,andnototherpropertiesoftheaddedviscosogens,causesthedependenceofIETratesonthesolventconcentration.TheIETkineticsresultsindicatethattheFMN–hemeIETiniNOSisgatedbyalargeconformationalchangeoftheFMNdomain.ThekineticsandNOSflavinfluorescenceresultstogetherindicatethatthedockedFMN/hemestateispopulatedtransiently...