Binding of imidazole to the heme of cytochrome c1 and inhibition of the bc1 complex from Rhodobacter sphaeroides: II. Kinetics and mechanism of binding.

ABSTRACT: The kinetics of imidazole (Im) and N-methylimidazole (MeIm) binding to oxidized cytochrome (cyt) c(1) of detergent-solubilized bc(1) complex from Rhodobacter sphaeroides are described. The rate of formation of the cyt c(1)-Im complex exhibited three separated regions of dependence on the concentration of imidazole: (i) below 8 mM Im, the rate increased with concentration in a parabolic manner; (ii) above 20 mM, the rate leveled off, indicating a rate-limiting conformational step with lifetime approximately 1 s; and (iii) at Im concentrations above 100 mM, the rate substantially increased again, also parabolically. In contrast, binding of MeIm followed a simple hyperbolic concentration dependence. The temperature dependences of the binding and release kinetics of Im and MeIm were also measu

SUBMITTER: Kokhan O 

PROVIDER: S-EPMC2903381 | biostudies-literature | 2010 Jul

REPOSITORIES: biostudies-literature