title: Translocator proteins in the two-partner secretion family have multiple domains.
abstract: The two-partner secretion pathway in Gram-negative bacteria consists of a TpsA exoprotein and a cognate TpsB outer membrane translocator protein. Previous work has demonstrated that the TpsB protein forms a beta-barrel structure with pore forming activity and facilitates translocation of the TpsA protein across the outer membrane. In this study, we characterized the functional domains of the Haemophilus influenzae HMW1B protein, a TpsB protein that interacts with the H. influenzae HMW1 adhesin. Using c-Myc epitope tag insertions and cysteine substitution mutagenesis, we discovered that HMW1B contains an N-terminal surface-localized domain, an internal periplasmic domain, and a C-terminal membrane anchor. Functional and biochemical analysis of the c-Myc epitope tag insertions and a series of HMW1B deletion constructs demonstrated that the periplasmic domain is required for secretion of HMW1 and that the C-terminal membrane anchor (HMW1B-(234-545)) is capable of oligomerization and pore formation. Similar to our observations with HMW1B, examination of a Bordetella pertussis TpsB protein called FhaC revealed that the C terminus of FhaC (FhaC-(232-585)) is capable of pore formation. We speculate that all TpsB proteins have a modular structure, with a periplasmic domain that interacts with the cognate TpsA protein and with pore forming activity contained within the C terminus.
authors.affiliation: The Edward Mallinckrodt Department of Pediatrics and the Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO 63110, USA.
authors.forename: Neeraj K
authors.initials: NK
authors.lastname: Surana
authors.forename: Amy Z
authors.initials: AZ
authors.lastname: Buscher
authors.forename: Gail G
authors.initials: GG
authors.lastname: Hardy
authors.forename: Susan
authors.initials: S
authors.lastname: Grass
authors.forename: Thomas
authors.initials: T
authors.lastname: Kehl-Fie
authors.forename: Joseph W
authors.initials: JW
authors.lastname: St Geme
mesh_terms: D018829:Adhesins, Bacterial / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D006193:Haemophilus influenzae / Q000502:physiology*; D008969:Molecular Sequence Data; D016296:Mutagenesis; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary
chemical_list: D018829:Adhesins, Bacterial; D001425:Bacterial Outer Membrane Proteins; C117431:HMW1 protein, bacteria; C117432:HMW2 protein, bacteria