title: Functional and phylogenetic properties of the pore-forming beta-barrel transporters of the Omp85 family.
abstract: beta-Barrel-shaped channels of the Omp85 family are involved in the translocation or assembly of proteins of bacterial, mitochondrial, and plastidic outer membranes. We have compared these proteins to understand the evolutionary development of the translocators. We have demonstrated that the proteins from proteobacteria and mitochondria have a pore diameter that is at least five times smaller than found for the Omp85 in cyanobacteria and plastids. This finding can explain why Omp85 from cyanobacteria (but not the homologous protein from proteobacteria) was remodeled to become the protein translocation pore after endosymbiosis. Further, the pore-forming region of the Omp85 proteins is restricted to the C terminus. Based on a phylogenetic analysis we have shown that the pore-forming domain displays a different evolutionary relationship than the N-terminal domain. In line with this, the affinity of the N-terminal domain to the C-terminal region of the Omp85 from plastids and cyanobacteria differs, even though the N-terminal domain is involved in gating of the pore in both groups. We have further shown that the N-terminal domain of nOmp85 takes part in homo-oligomerization. Thereby, the differences in the phylogeny of the two domains are explained by different functional constraints acting on the regions. The pore-forming domain, however, is further divided into two functional regions, where the distal C terminus itself forms a dimeric pore. Based on functional and phylogenetic analysis, we suggest an evolutionary scenario that explains the origin of the contemporary translocon.
authors.affiliation: Ludwig Maximilians University (LMU), Department of Biology I, Menzinger Strasse 67, 80638 München, Germany.
authors.forename: Rolf
authors.initials: R
authors.lastname: Bredemeier
authors.forename: Thomas
authors.initials: T
authors.lastname: Schlegel
authors.forename: Franziska
authors.initials: F
authors.lastname: Ertel
authors.forename: Aleksandar
authors.initials: A
authors.lastname: Vojta
authors.forename: Ljudmila
authors.initials: L
authors.lastname: Borissenko
authors.forename: Markus T
authors.initials: MT
authors.lastname: Bohnsack
authors.forename: Michael
authors.initials: M
authors.lastname: Groll
authors.forename: Arndt
authors.initials: A
authors.lastname: von Haeseler
authors.forename: Enrico
authors.initials: E
authors.lastname: Schleiff
mesh_terms: D000818:Animals; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry* / Q000502:physiology*; D003432:Cross-Linking Reagents / Q000494:pharmacology; D029721:Drosophila Proteins / Q000737:chemistry; D004331:Drosophila melanogaster; D004594:Electrophysiology; D029968:Escherichia coli Proteins / Q000737:chemistry; D019143:Evolution, Molecular; D015964:Gene Expression Regulation, Bacterial; D008954:Models, Biological; D046937:Nostoc / Q000378:metabolism*; D010802:Phylogeny; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D016601:RNA-Binding Proteins / Q000737:chemistry
chemical_list: D001425:Bacterial Outer Membrane Proteins; C503914:BamA protein, E coli; D003432:Cross-Linking Reagents; D029721:Drosophila Proteins; D029968:Escherichia coli Proteins; D016601:RNA-Binding Proteins; C490833:qkr54B protein, Drosophila