title: Discovery of a novel periplasmic protein that forms a complex with a trimeric autotransporter adhesin and peptidoglycan.
abstract: Trimeric autotransporter adhesins (TAAs), fibrous proteins on the cell surface of Gram-negative bacteria, have attracted attention as virulence factors. However, little is known about the mechanism of their biogenesis. AtaA, a TAA of Acinetobacter sp. Tol 5, confers nonspecific, high adhesiveness to bacterial cells. We identified a new gene, tpgA, which forms a single operon with ataA and encodes a protein comprising two conserved protein domains identified by Pfam: an N-terminal SmpA/OmlA domain and a C-terminal OmpA_C-like domain with a peptidoglycan (PGN)-binding motif. Cell fractionation and a pull-down assay showed that TpgA forms a complex with AtaA, anchoring it to the outer membrane (OM). Isolation of total PGN-associated proteins showed TpgA binding to PGN. Disruption of tpgA significantly decreased the adhesiveness of Tol 5 because of a decrease in surface-displayed AtaA, suggesting TpgA involvement in AtaA secretion. This is reminiscent of SadB, which functions as a specific chaperone for SadA, a TAA in Salmonella species; however, SadB anchors to the inner membrane, whereas TpgA anchors to the OM through AtaA. The genetic organization encoding the TAA-TpgA-like protein cassette can be found in diverse Gram-negative bacteria, suggesting a common contribution of TpgA homologues to TAA biogenesis.
authors.affiliation: Department of Biotechnology, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi, 464-8603, Japan.
authors.forename: Masahito
authors.initials: M
authors.lastname: Ishikawa
authors.affiliation: Department of Biotechnology, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi, 464-8603, Japan.
authors.forename: Shogo
authors.initials: S
authors.lastname: Yoshimoto
authors.affiliation: Department of Biotechnology, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi, 464-8603, Japan.
authors.forename: Ayumi
authors.initials: A
authors.lastname: Hayashi
authors.affiliation: Department of Biotechnology, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi, 464-8603, Japan.
authors.forename: Junichi
authors.initials: J
authors.lastname: Kanie
authors.affiliation: Department of Biotechnology, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi, 464-8603, Japan.
authors.forename: Katsutoshi
authors.initials: K
authors.lastname: Hori
mesh_terms: D000150:Acinetobacter / Q000378:metabolism*; D018829:Adhesins, Bacterial / Q000096:biosynthesis / Q000378:metabolism*; D002473:Cell Wall / Q000378:metabolism; D018832:Molecular Chaperones / Q000378:metabolism; D010457:Peptidoglycan / Q000378:metabolism*; D019897:Periplasm / Q000378:metabolism; D033903:Periplasmic Proteins / Q000378:metabolism; D020539:Sequence Analysis, Protein; D000069320:Type V Secretion Systems / Q000378:metabolism; D037521:Virulence Factors / Q000378:metabolism
chemical_list: D018829:Adhesins, Bacterial; D018832:Molecular Chaperones; D010457:Peptidoglycan; D033903:Periplasmic Proteins; D000069320:Type V Secretion Systems; D037521:Virulence Factors