The possible role of isoforms of cytochrome c oxidase subunit VIa in mammalian thermogenesis

A single cDNA of cytochrome c oxidase subunit VIa was characterised from liver, heart and the thermogenic organ of the partially endotherm tuna fish. The amino acid sequence revealed high identity with subunit VIa from carp and trout, but low identity to subunits VIaL (liver type) and VIaH (heart type) of mammalian cytochrome c oxidase. In reconstituted cytochrome c oxidase from bovine heart, the H ⁺/e⁻ stoichiometry is decreased from 1.0 to 0.5 at high intraliposomal ATP/ADP ratios via exchange of bound ADP by ATP at the matrix domain of the transmembraneous subunit VIaH. Reconstituted cytochrome c oxidase from bovine liver and kidney, containing subunit VIaL, revealed H ⁺/e⁻ ratios below 0.5, independent of the ATP/ADP ratio. The results suggest the evolution of three types of subunit VIa. Subunits VIaH and VIaL are postulated to participate in mammalian thermogenesis. Received 3 May 1999; received after revision 10 June 1999; accepted 29 June 1999     

冷暴露过程中高原鼠兔的产热变化

探讨了高原鼠免在冷暴露过程中静止代谢率（RMR）,非颤抖性产热（NST）的变化．同时观察肝脏褐色脂肪组织（BAT）线粒体蛋白等指标的变化,表明高原鼠兔对环境温度的适应是通过整体产热和细胞产热的改变来维持其恒定的体温．