摘要：SummaryThe first steroidogenic enzyme, cytochrome P450-side-chain-cleavage (SCC), requires electron transport chain (ETC) complexes III and IV to initiate steroid metabolic processes for mammalian survival. ETC complex II, containing succinate dehydrogenase (quinone), acts with the TCA cycle and has no proton pumping capacity. We show that complex II is required for SCC activation through the proton pump, generating an intermediate state for addition of phosphate by succinate. Phosphate anions in the presence of succinate form a stable mitochondrial complex with higher enthalpy (-ΔH) and enhanced activity. Inhibition of succinate action prevents SCC processing at the intermediate state and ablates activity and mitochondrial protein network. This is the first report directly showing that a protein intermediate state is activated by succinate, facilitating the ETC complex II to interact with complexes III and IV for continued mitochondrial metabolic process, suggesting complex II is essential for steroid metabolism regulation.Graphical AbstractDisplay OmittedHighlights•P450 SCC synthesizes first steroid with the electrons from ETC complex III to IV•Succinate from complex II activates complex III for the metabolic activity•Absence of succinate ablates mitochondrial processing of SCC and metabolic activity•Succinate anion stabilizes ETC complex II for the activation of steroid metabolismBiological Sciences; Biochemistry; Molecular Biology
