Intimin-mediated export of passenger proteins requires maintenance of a translocation-competent conformation.
Intimins from pathogenic bacteria promote intimate bacterial adhesion to epithelial cells. Several structurally similar domains form on the bacterial cell surface an extended rigid rod that exposes the carboxy-terminal domain, which interacts with the translocated intimin receptor. We constructed a series of intimin-derived fusion proteins consisting of carboxy-terminally truncated intimin and the immunoglobulin light-chain variable domain REIv, ubiquitin, calmodulin, beta-lactamase inhibitor protein, or beta-lactamase. By systematically investigating the intimin-mediated cell surface exposure of these passenger domains in the presence or absence of compounds that interfere with outer membrane stability or passenger domain folding, we acquired experimental evidence that intimin-mediated protein export across the outer membrane requires, prior to export, the maintenance of a translocation-competent conformation that may be distinct from the final protein structure. We propose that, during export, competition exists between productive translocation and folding of the passenger domain in the periplasm into a stable conformation that is not compatible with translocation through the bacterial outer membrane. These results may expand understanding of the mechanism by which intimins are inserted into the outer membrane and expose extracellular domains on the cell surface.
Adams
Thorsten M
TM
Abteilung für Molekulare Genetik und Präparative Molekularbiologie, Institut für Mikrobiologie und Genetik, Georg-August-Universität Göttingen, Grisebachstr. 8, D-37077 Göttingen, Germany.
Wentzel
Alexander
A
Kolmar
Harald
H
D018829:Adhesins, Bacterial / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D001422:Bacterial Adhesion; D002147:Calmodulin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D019453:Escherichia coli O157 / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D007147:Immunoglobulin Light Chains / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011487:Protein Conformation; D017510:Protein Folding; D021381:Protein Transport; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D025801:Ubiquitin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D001618:beta-Lactamases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
D018829:Adhesins, Bacterial; D002147:Calmodulin; D029968:Escherichia coli Proteins; D007147:Immunoglobulin Light Chains; D011993:Recombinant Fusion Proteins; D025801:Ubiquitin; C073819:eaeA protein, E coli; D001618:beta-Lactamases