title: Solving Kinetic Equations for the Laser Flash Photolysis Experiment on Nitric Oxide Synthases: Effect of Conformational Dynamics on the Interdomain Electron Transfer.
abstract: The production of nitric oxide by the nitric oxide synthase (NOS) enzyme depends on the interdomain electron transfer (IET) between the flavin mononucleotide (FMN) and heme domains. Although the rate of this IET has been measured by laser flash photolysis (LFP) for various NOS proteins, no rigorous analysis of the relevant kinetic equations was performed so far. In this work, we provide an analytical solution of the kinetic equations underlying the LFP approach. The derived expressions reveal that the bulk IET rate is significantly affected by the conformational dynamics that determines the formation and dissociation rates of the docking complex between the FMN and heme domains. We show that in order to informatively study the electron transfer across the NOS enzyme, LFP should be used in combination with other spectroscopic methods that could directly probe the docking equilibrium and the conformational change rate constants. The implications of the obtained analytical expressions for the interpretation of the LFP results from various native and modified NOS proteins are discussed. The mathematical formulas derived in this work should also be applicable for interpreting the IET kinetics in other modular redox enzymes.
authors.affiliation: Department of Chemistry and Biochemistry, University of Arizona , Tucson, Arizona 85721, United States.
authors.forename: Andrei V
authors.initials: AV
authors.lastname: Astashkin
authors.affiliation: Department of Pharmaceutical Sciences, College of Pharmacy, University of New Mexico , Albuquerque, New Mexico 87131, United States.
authors.forename: Changjian
authors.initials: C
authors.lastname: Feng
mesh_terms: D000818:Animals; D002248:Carbon Monoxide / Q000737:chemistry; D004583:Electrons; D006418:Heme / Q000737:chemistry; D006801:Humans; D007700:Kinetics; D007834:Lasers; D051379:Mice; D009154:Mutation; D009569:Nitric Oxide / Q000737:chemistry; D019001:Nitric Oxide Synthase / Q000737:chemistry* / Q000235:genetics; D010782:Photolysis; D011487:Protein Conformation; D051381:Rats
chemical_list: D009569:Nitric Oxide; D006418:Heme; D002248:Carbon Monoxide; D019001:Nitric Oxide Synthase