Murburn scheme for mitochondrial thermogenesis

Abstract

The physiology of thermogenesis in mitochondria (mediated by uncoupling protein, UCP) has traditionally been explained as the dissipation of proton gradient across the inner mitochondrial membrane into heat. However, there are differences of opinion on how thermogenesis is achieved by UCPs and the mechanistic theories have not been correlated sufficiently with UCP’s structure. Recent experimental evidence suggests strong correlation of diffusible reactive oxygen species (DROS) with UCP-induced thermogenesis. Further, the mechanistic explanations of mitochondrial oxidative phosphorylation (mOxPhos) were recently revamped with murburn concept, which considers DROS as an obligatory catalytic agent in mOxPhos. Herein, we propose that UCPs (aided by the large pore and positively charged amino acids of aqueous-phase loops) enable protonation and transport of DROS. Thus, UCP facilitates DROS-reactions amongst themselves, forming water and liberating heat around the inner mitochondrial membrane. Thereby, the simple murburn scheme for biothermogenesis integrates structural information of UCP with its attributed physiological function.