Formation of electrostatically-stabilized complex at low ionic strength [formula omitted] interprotein electron transfer between yeast cytochrome [formula omitted] and cytochrome [formula omitted] peroxidase

Abstract

Electron transfer from yeast ferrous cytochrome c to H 2O 2-oxidized yeast cytochrome c peroxidase has been studied using flash photoreduction methods. At low ionic strength (μ < 10 mM), where a strong complex is formed between cytochrome c and peroxidase, electron transfer occurs rather slowly (k ∼ 200s −1). However, at high ionic strength where the electrostatic complex is largely dissociated, the observed first-order rate constant for peroxidase reduction increases significantly reaching a concentration independent limit of k ∼1500 s −1. Thus, at least in some cases, formation of an electrostatically-stabilized complex can actually impede electron transfer between proteins.