title: Targeting of Yersinia Yop proteins into the cytosol of HeLa cells: one-step translocation of YopE across bacterial and eukaryotic membranes is dependent on SycE chaperone.
abstract: Pathogenic Yersiniae adhere to and kill macrophages by targeting some of their Yop proteins into the eukaryotic cytosol. There is debate about whether YopE targeting proceeds as a direct translocation of polypeptide between cells or in two distinct steps, each requiring specific signals for YopE secretion across the bacterial envelope and for translocation into the eukaryotic cytosol. Here, we used the selective solubilization of the eukaryotic plasma membrane with digitonin to measure Yop targeting during Yersinia infections of HeLa cells. YopE, YopH, YopM and YopN were found in the eukaryotic cytosol but not in the extracellular medium. When bound to SycE chaperone in the Yersinia cytoplasm, YopE residues 1-100 are necessary and sufficient for the targeting of hybrid neomycin phosphotransferase. Electron microscopic analysis failed to detect an extracellular intermediate of YopE targeting, suggesting a one-step translocation mechanism.
authors.affiliation: Department of Microbiology and Immunology, UCLA School of Medicine, University of California, Los Angeles 90095, USA.
authors.forename: V T
authors.initials: VT
authors.lastname: Lee
authors.forename: D M
authors.initials: DM
authors.lastname: Anderson
authors.forename: O
authors.initials: O
authors.lastname: Schneewind
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism*; D004072:Digitonin; D019084:Fluorescent Antibody Technique, Indirect; D006367:HeLa Cells; D006801:Humans; D019868:Kanamycin Kinase / Q000235:genetics; D008565:Membrane Proteins; D016253:Microscopy, Immunoelectron; D010957:Plasmids; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015398:Signal Transduction; D015534:Trans-Activators / Q000378:metabolism*; D015007:Yersinia / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity*
chemical_list: D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D008565:Membrane Proteins; D011993:Recombinant Fusion Proteins; C081269:SycE protein, Yersinia; D015534:Trans-Activators; C063239:yopE protein, Yersinia; C070015:YopN protein, Yersinia; D019868:Kanamycin Kinase; D004072:Digitonin