tailieunhanh - Báo cáo khoa học: Mitochondrial connection to the origin of the eukaryotic cell

Phylogenetic evidence is presented that primitively amito-chondriate eukaryotes containing the nucleus, cytoskele-ton, and endomembrane system may have never existed. Instead, the primary host for the mitochondrial progeni-tor may have been a chimeric prokaryote, created by fusion between an archaebacterium and a eubacterium, in which eubacterial energy metabolism (glycolysis and fermentation) was retained. | Eur. J. Biochem. 270 1599-1618 2003 FEBS 2003 doi REVIEW ARTICLE Mitochondrial connection to the origin of the eukaryotic cell Victor V. Emelyanov Gamaleya Institute of Epidemiology and Microbiology Moscow Russia Phylogenetic evidence is presented that primitively amito-chondriate eukaryotes containing the nucleus cytoskeleton and endomembrane system may have never existed. Instead the primary host for the mitochondrial progenitor may have been a chimeric prokaryote created by fusion between an archaebacterium and a eubacterium in which eubacterial energy metabolism glycolysis and fermentation was retained. A Rickettsia-like intracellular symbiont suggested to be the last common ancestor of the family Rickettsiaceae and mitochondria may have penetrated such a host pro-eukaryote surrounded by a single membrane due to tightly membrane-associated phospholipase activity as do present-day rickettsiae. The relatively rapid evolutionary conversion of the invader into an organelle may have occurred in a safe milieu via numerous often dramatic changes involving both partners which resulted in successful coupling of the host glycolysis and the symbiont respiration. Establishment of a potent energy-generating organelle made it possible through rapid dramatic changes to develop genuine eukaryotic elements. Such sequential or converging global events could fill the gap between prokaryotes and eukaryotes known as major evolutionary discontinuity. Keywords endosymbiotic origin energy metabolism mitochondrial ancestor respiration rickettsiae fusion hypothesis eukaryogenesis phylogenetic analysis paralogous protein family. From a genomics perspective it is clear that both archae-bacteria domain Archaea and eubacteria domain Bacteria contributed substantially to eukaryotic genomes 1-7 . It is also evident that eukaryotes domain Eukarya acquired eubacterial genes from a single mitochondrial ancestor during endosymbiosis 8-14 which probably occurred .