title: Assembly factor Omp85 recognizes its outer membrane protein substrates by a species-specific C-terminal motif.
abstract: Integral beta-barrel proteins are found in the outer membranes of Gram-negative bacteria, mitochondria, and chloroplasts. The assembly of these proteins requires a proteinaceous apparatus of which Omp85 is an evolutionary conserved central component. To study its molecular mechanism, we have produced Omp85 from Escherichia coli in inclusion bodies and refolded it in vitro. The interaction of Omp85 with its substrate proteins was studied in lipid-bilayer experiments, where it formed channels. The properties of these channels were affected upon addition of unfolded outer-membrane proteins (OMPs) or synthetic peptides corresponding to their C-terminal signature sequences. The interaction exhibited species specificity, explaining the inefficient assembly of OMPs from Neisseria in E. coli. Accordingly, the in vivo assembly of the neisserial porin PorA into the E. coli outer membrane was accomplished after adapting its signature sequence. These results demonstrate that the Omp85 assembly machinery recognizes OMPs by virtue of their C-terminal signature sequence.
authors.affiliation: Department of Molecular Microbiology and Institute of Biomembranes, Utrecht University, Utrecht, The Netherlands.
authors.forename: Viviane
authors.initials: V
authors.lastname: Robert
authors.forename: Elena B
authors.initials: EB
authors.lastname: Volokhina
authors.forename: Freya
authors.initials: F
authors.lastname: Senf
authors.forename: Martine P
authors.initials: MP
authors.lastname: Bos
authors.forename: Patrick
authors.initials: P
authors.lastname: Van Gelder
authors.forename: Jan
authors.initials: J
authors.lastname: Tommassen
mesh_terms: D020816:Amino Acid Motifs / Q000502:physiology; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry / Q000378:metabolism* / Q000502:physiology; D004926:Escherichia coli / Q000502:physiology; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000502:physiology*; D002479:Inclusion Bodies / Q000737:chemistry; D007473:Ion Channels / Q000737:chemistry / Q000378:metabolism; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology; D046912:Multiprotein Complexes / Q000378:metabolism; D011485:Protein Binding; D017510:Protein Folding; D021382:Protein Sorting Signals / Q000502:physiology; D017434:Protein Structure, Tertiary; D013045:Species Specificity
chemical_list: D001425:Bacterial Outer Membrane Proteins; C503914:BamA protein, E coli; D029968:Escherichia coli Proteins; D007473:Ion Channels; D008565:Membrane Proteins; D046912:Multiprotein Complexes; C115176:Omp85 protein, Neisseria; D021382:Protein Sorting Signals