Satyamjayatu: The Science & Ethics Foundation, Kulappully, Shoranur-2 (PO), Palakkad, Kerala, 679122, India.
Department of Biotechnology, Vignan's Foundation for Science, Technology & Research, Vadlamudi, Guntur, 522213, India.
Cell Biochem Biophys. 2021 Mar;79(1):3-10. doi: 10.1007/s12013-020-00945-y. Epub 2020 Sep 29.
Quinones are found in the lipid membranes of prokaryotes like E. coli and cyanobacteria, and are also abundant in eukaryotic mitochondria and chloroplasts. They are intricately involved in the reaction mechanism of redox phosphorylations. In the Mitchellian chemiosmotic school of thought, membrane-lodged quinones are perceived as highly mobile conveyors of two-electron equivalents from the first leg of Electron Transport Chain (ETC) to the 'second pit-stop' of Cytochrome bc or bf complex (CBC), where they undergo a regenerative 'Q-cycle'. In Manoj's murburn mechanism, the membrane-lodged quinones are perceived as relatively slow-moving one- or two- electron donors/acceptors, enabling charge separation and the CBC resets a one-electron paradigm via 'turbo logic'. Herein, we compare various purviews of the two mechanistic schools with respect to: constraints in mobility, protons' availability, binding of quinones with proteins, structural features of the protein complexes, energetics of reaction, overall reaction logic, etc. From various perspectives, the murburn mechanism appeals as a viable alternative explanation well-rooted in thermodynamics/kinetics and one which lends adequate structure-function correlations for the roles of quinones, lipid membrane and associated proteins.
醌类化合物存在于原核生物（如大肠杆菌和蓝藻）的脂膜中，也大量存在于真核生物的线粒体和叶绿体中。它们在氧化还原磷酸化反应机制中起着错综复杂的作用。在米切尔的化学渗透学派中，膜结合的醌类化合物被认为是从电子传递链（ETC）的第一阶段到细胞色素 bc 或 bf 复合物（CBC）的“第二个停靠点”的两个电子等当量的高度移动载体，在那里它们经历一个再生的“Q 循环”。在马诺杰的默伯恩机制中，膜结合的醌类化合物被认为是相对缓慢的单电子或双电子供体/受体，能够实现电荷分离，并且 CBC 通过“涡轮逻辑”重置单电子范例。在这里，我们比较了这两种机制学派的各种观点，包括：在移动性、质子可用性、醌与蛋白质的结合、蛋白质复合物的结构特征、反应能学、整体反应逻辑等方面的限制。从各个角度来看，默伯恩机制作为一种可行的替代解释，它根植于热力学/动力学，并且为醌类化合物、脂膜和相关蛋白质的作用提供了充分的结构-功能相关性。
