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Evidence for a novel domain of bacterial outer membrane ushers
Author(s) -
Capitani Guido,
Eidam Oliv,
Grütter Markus G.
Publication year - 2006
Publication title -
proteins: structure, function, and bioinformatics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.699
H-Index - 191
eISSN - 1097-0134
pISSN - 0887-3585
DOI - 10.1002/prot.21147
Subject(s) - periplasmic space , bacterial outer membrane , pilus , chaperone (clinical) , transmembrane protein , transmembrane domain , thermus thermophilus , biogenesis , microbiology and biotechnology , biology , chemistry , biochemistry , escherichia coli , membrane , medicine , receptor , pathology , gene
Many pathogenic bacteria possess adhesive surface organelles (called pili), anchored to their outer membrane, which mediate the first step of infection by binding to host tissue. Pilus biogenesis occurs via the “chaperone–usher” pathway: the usher, a large outer membrane protein, binds complexes of a periplasmic chaperone with pilus subunits, unloads the subunits from the chaperone, and assembles them into the pilus, which is extruded into the extracellular space. Ushers comprise an N‐terminal periplasmic domain, a large transmembrane β‐barrel central domain, and a C‐terminal periplasmic domain. Since structural data are available only for the N‐terminal domain, we performed an in‐depth bioinformatic analysis of bacterial ushers. Our analysis led us to the conclusion that the transmembrane β‐barrel region of ushers contains a so far unrecognized soluble domain, the “middle domain”, which possesses a β‐sandwich fold. Two other bacterial β‐sandwich domains, the TT0351 protein from Thermus thermophilus and the carbohydrate binding module CBM36 from Paenibacillus polymyxa , are possible distant relatives of the usher “middle domain”. Several mutations reported to abolish in vivo pilus formation cluster in this region, underlining its functional importance. Proteins 2006. © 2006 Wiley‐Liss, Inc.