title: A trimeric lipoprotein assists in trimeric autotransporter biogenesis in enterobacteria.
abstract: Trimeric autotransporter adhesins (TAAs) are important virulence factors of many Gram-negative bacterial pathogens. TAAs form fibrous, adhesive structures on the bacterial cell surface. Their N-terminal extracellular domains are exported through a C-terminal membrane pore; the insertion of the pore domain into the bacterial outer membrane follows the rules of β-barrel transmembrane protein biogenesis and is dependent on the essential Bam complex. We have recently described the full fiber structure of SadA, a TAA of unknown function in Salmonella and other enterobacteria. In this work, we describe the structure and function of SadB, a small inner membrane lipoprotein. The sadB gene is located in an operon with sadA; orthologous operons are only found in enterobacteria, whereas other TAAs are not typically associated with lipoproteins. Strikingly, SadB is also a trimer, and its co-expression with SadA has a direct influence on SadA structural integrity. This is the first report of a specific export factor of a TAA, suggesting that at least in some cases TAA autotransport is assisted by additional periplasmic proteins.
authors.affiliation: From the Max Planck Institut für Entwicklungsbiologie, 72076 Tübingen.
authors.forename: Iwan
authors.initials: I
authors.lastname: Grin
authors.forename: Marcus D
authors.initials: MD
authors.lastname: Hartmann
authors.forename: Guido
authors.initials: G
authors.lastname: Sauer
authors.forename: Birte
authors.initials: B
authors.lastname: Hernandez Alvarez
authors.forename: Monika
authors.initials: M
authors.lastname: Schütz
authors.forename: Samuel
authors.initials: S
authors.lastname: Wagner
authors.forename: Johannes
authors.initials: J
authors.lastname: Madlung
authors.forename: Boris
authors.initials: B
authors.lastname: Macek
authors.forename: Alfonso
authors.initials: A
authors.lastname: Felipe-Lopez
authors.forename: Michael
authors.initials: M
authors.lastname: Hensel
authors.forename: Andrei
authors.initials: A
authors.lastname: Lupas
authors.forename: Dirk
authors.initials: D
authors.lastname: Linke
mesh_terms: D018829:Adhesins, Bacterial / Q000235:genetics / Q000378:metabolism; D001692:Biological Transport; D002469:Cell Separation; D003001:Cloning, Molecular; D017931:DNA Primers; D004755:Enterobacteriaceae / Q000378:metabolism*; D005434:Flow Cytometry; D008074:Lipoproteins / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D019151:Peptide Library; D019897:Periplasm / Q000378:metabolism; D010957:Plasmids / Q000378:metabolism; D055503:Protein Multimerization; D017434:Protein Structure, Tertiary; D012475:Salmonella / Q000378:metabolism*; D013499:Surface Properties
chemical_list: D018829:Adhesins, Bacterial; D017931:DNA Primers; D008074:Lipoproteins; D019151:Peptide Library
keywords: Autotransport; Bacterial Adhesion; Bacterial Pathogenesis; Crystal Structure; Enterobacteria; Gram-negative Bacteria; Lipoprotein; Membrane Insertion; Membrane Trafficking