title: The α-barrel tip region of Escherichia coli TolC homologs of Vibrio vulnificus interacts with the MacA protein to form the functional macrolide-specific efflux pump MacAB-TolC.
abstract: TolC and its homologous family of proteins are outer membrane factors that are essential for exporting small molecules and toxins across the outer membrane in Gram-negative bacteria. Two open reading frames in the Vibrio vulnificus genome that encode proteins homologous to Escherichia coli TolC, designated TolCV1 and TolCV2, have 51.3% and 29.6% amino acid identity to TolC, respectively. In this study, we show that TolCV1 and TolCV2 functionally and physically interacted with the membrane fusion protein, MacA, a component of the macrolide-specific MacAB-TolC pump of E. coli. We further show that the conserved residues located at the aperture tip region of the α-hairpin of TolCV1 and TolCV2 played an essential role in the formation of the functional MacAB-TolC pump using site-directed mutational analyses. Our findings suggest that these outer membrane factors have conserved tip-to-tip interaction with the MacA membrane fusion protein for action of the drug efflux pump in Gram-negative bacteria.
authors.affiliation: Department of Life Science, Chung-Ang University, Seoul 156-756, Republic of Korea.
authors.forename: Minho
authors.initials: M
authors.lastname: Lee
authors.forename: Hyun-Lee
authors.initials: HL
authors.lastname: Kim
authors.forename: Saemee
authors.initials: S
authors.lastname: Song
authors.forename: Minju
authors.initials: M
authors.lastname: Joo
authors.forename: Seunghwa
authors.initials: S
authors.lastname: Lee
authors.forename: Daeyoung
authors.initials: D
authors.lastname: Kim
authors.forename: Yoonsoo
authors.initials: Y
authors.lastname: Hahn
authors.forename: Nam-Chul
authors.initials: NC
authors.lastname: Ha
authors.forename: Kangseok
authors.initials: K
authors.lastname: Lee
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D000900:Anti-Bacterial Agents / Q000378:metabolism*; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D018942:Macrolides / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D017433:Protein Structure, Secondary; D016415:Sequence Alignment; D013045:Species Specificity; D041261:Vibrio vulnificus / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D018528:ATP-Binding Cassette Transporters; D000900:Anti-Bacterial Agents; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D018942:Macrolides; D026901:Membrane Transport Proteins; C073126:tolC protein, E coli