Electron transfer amongst flavo- and hemo-proteins: diffusible species effect the relay processes, not protein–protein binding

摘要: Hitherto, electron transfer (ET) between redox proteins has been deemed to occur via donor–acceptor binding, and diffusible reactive species are considered as deleterious side-products in such systems. Herein, ET from cytochrome P450 reductase (CPR, an animal membrane flavoprotein) horseradish peroxidase (HRP, a plant hemoprotein) c (Cyt c, soluble was probed under diverse conditions, using standard assays. the CPR-Cyt system critically inhibited by cyanide sub-equivalent levels of polar one-electron cyclers like copper ions, vitamin C/Trolox superoxide dismutase. In presence lipids, inhibition also afforded amphipathic molecules E, palmitoyl-vitamin C hemoprotein, b5. Such non-specific (by agents both aqueous lipid phases) indicated that transfer/relay effected small agents, whose lifetimes shortened radical scavengers. When CPR retained dialysis Cyt presented outside free solution, still observed. Further, HRP (taken at nM levels) catalyzed oxidation phenolic substrate significantly upon incorporation sub-nM c. The findings imply or HRP-Cyt binding is not crucial for ET. fundamental quantitative arguments (based on diffusion/collision) challenge erstwhile protein–protein binding-assisted hypothesis. It proven beyond reasonable doubt mobile carriers (ions radicals) serve “redox-relay agents” biological models/setup studied.