title: Protein secretion in gram-negative bacteria: assembly of the three components of ABC protein-mediated exporters is ordered and promoted by substrate binding.
abstract: One of the strategies used by Gram-negative bacteria to secrete proteins across the two membranes which delimit the cells, is sec independent and dedicated to proteins lacking an N-terminal signal peptide. It depends on ABC protein-mediated exporters, which consist of three cell envelope proteins, two inner membrane proteins, an ATPase (the ABC protein), a membrane fusion protein (MFP) and an outer membrane polypeptide. Erwinia chrysanthemi metalloproteases B and C and Serratia marcescens hemoprotein HasA are secreted by such homologous pathways and interact with the ABC protein. Using as protein substrates HasA and GST-PrtC, a chimeric protein which has a glutathione S-transferase moiety fused to a large C-terminal domain of protease C, we developed a simple system to identify proteins bound to the substrate based on substrate affinity-chromatography using heme- or glutathione-agarose. We show an ordered association between the protein substrates and the three exporter components: the substrate recognizes the ABC protein which interacts with the MFP which in turn binds the outer membrane component. Substrate binding is required for assembly of the three components.
authors.affiliation: Unité de Physiologie Cellulaire, Institut Pasteur, URA 1300, CNRS, Paris, France.
authors.forename: S
authors.initials: S
authors.lastname: Létoffé
authors.forename: P
authors.initials: P
authors.lastname: Delepelaire
authors.forename: C
authors.initials: C
authors.lastname: Wandersman
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000737:chemistry / Q000378:metabolism*; D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism*; D001665:Binding Sites; D001693:Biological Transport, Active; D002352:Carrier Proteins; D017364:Collagenases / Q000378:metabolism; D016974:Dickeya chrysanthemi / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D006090:Gram-Negative Bacteria / Q000235:genetics / Q000378:metabolism*; D046911:Macromolecular Substances; D008565:Membrane Proteins / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012706:Serratia marcescens / Q000235:genetics / Q000378:metabolism
chemical_list: D018528:ATP-Binding Cassette Transporters; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D002352:Carrier Proteins; C093956:HasA protein, Serratia marcescens; D046911:Macromolecular Substances; D008565:Membrane Proteins; C090391:PrtD protein, Erwinia chrysanthemi; C093955:PrtF protein, bacteria; D011993:Recombinant Fusion Proteins; D017364:Collagenases; C074887:prtC protein, bacteria