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


Autoria(s): Manoj, Kelath Murali; Gade, Sudeep K; Venkatachalam, Avanthika; Gideon, Daniel A
Data(s)

2016

Resumo

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) and horseradish peroxidase (HRP, a plant hemoprotein) to cytochrome c (Cyt c, a soluble animal hemoprotein) was probed under diverse conditions, using standard assays. ET in the CPR-Cyt c system was critically inhibited by cyanide and sub-equivalent levels of polar one-electron cyclers like copper ions, vitamin C/Trolox and superoxide dismutase. In the presence of lipids, inhibition was also afforded by amphipathic molecules vitamin E, palmitoyl-vitamin C and the membrane hemoprotein, cytochrome b(5). Such nonspecific inhibition (by diverse agents in both aqueous and lipid phases) indicated that electron transfer/relay was effected by small diffusible agents, whose lifetimes are shortened by the diverse radical scavengers. When CPR was retained in a dialysis membrane and Cyt c presented outside in free solution, ET was still observed. Further, HRP (taken at nM levels) catalyzed oxidation of a phenolic substrate was significantly inhibited upon the incorporation of sub-nM levels of Cyt c. The findings imply that CPR-Cyt c or HRP-Cyt c binding is not crucial for ET. Further, fundamental quantitative arguments (based on diffusion/collision) challenge the erstwhile protein-protein binding-assisted ET hypothesis. It is proven beyond reasonable doubt that mobile and diffusible electron carriers (ions and radicals) serve as ``redox-relay agents'' in the biological ET models/setup studied.

Formato

application/pdf

Identificador

http://eprints.iisc.ernet.in/53702/1/RSC_Adv_6-29_24121_2016.pdf

Manoj, Kelath Murali and Gade, Sudeep K and Venkatachalam, Avanthika and Gideon, Daniel A (2016) Electron transfer amongst flavo- and hemo-proteins: diffusible species effect the relay processes, not protein-protein binding. In: RSC ADVANCES, 6 (29). pp. 24121-24129.

Publicador

ROYAL SOC CHEMISTRY

Relação

http://dx.doi.org/10.1039/c5ra26122h

http://eprints.iisc.ernet.in/53702/

Palavras-Chave #Others
Tipo

Journal Article

PeerReviewed