The Study On Structural Basis And Functional Mechanism Of Uncoupling Proteins

Uncoupling proteins belong to the super family of mitochondrial anion carriers.They are transmembrane proteins that are located in the mitochondrial inner membrane.The primary function of uncoupling proteins is believed to be mediating the regulated protons leaks,and dissipate mitochondrial membrane potential generated by electron transport into heat.Uncoupling protein 1(UCP1)is an essential mitochondrial inner-membrane protein that regulates non-shivering thermogenesis and "browning" in endothermic animals.However,the precise mechanism by which uncoupling protein 1 mediates thermogenic proton leaks is still unclear.In the present study,a phylogenetic analysis shows that there is a significant increase in the evolutionary rate of vertebrate UCP1 when moving from marsupials to eutherians,and F128 and Y157 are found in all eutherian UCP1s but not in those of marsupials(1127 and F156).Biochemical studies show that rat and mouse UCP1s form a homo-dimer,and marsupial UCP,human UCP2,human UCP3 and human ANT do not form a homodimer.Interestingly,free fatty acids increase while GDP decrease UCP1 dimerization and proton leak activity.The mutant rUCPl(F128-S and Y157-M)completely loses its homodimeric structure and uncoupling activity.The reconstitution of rUCP1,but not marsupial UCP,in the brown adipose tissue of UCP1-KO mice completely rescues the body temperature drop that occurs under cold exposure,and mutant marsupial UCP(I127-F and F156-Y)has a partial rescue effect.In summary,it is clear that mitochondrial UCP1 is a monophyletic trait of eutherians.Dimerized eutherian UCP1 regulates thermogenic proton leaks,and only eutherians have real non-shivering thermogenesis and"browning".The current thesis focuses on the uncoupling-protein homologues,and was designed to study their structural basis or physiological function.The project explored the two scientific hypotheses:'UCP1 mediates proton leaks by the formation of homo-dimer' and 'UCP2 and the other mitochondrial protein carriers function as monomers'.