title: The N-terminal region of the 37-kDa translocated fragment of Pseudomonas exotoxin A aborts translocation by promoting its own export after microsomal membrane insertion.
abstract: The 37-kDa C-terminal fragment of Pseudomonas exotoxin A (PE; termed PE37 and composed of aa 280-613 of PE) translocates to the cell cytosol to cause cell death. PE37 requires a C-terminal endoplasmic reticulum retention sequence to be cytotoxic, indicating that the toxin may translocate to the cytosol from the endoplasmic reticulum. We show here that the N-terminal region of nascent PE37 can be inserted into the membrane of canine pancreatic microsomes by the preprocecropin signal sequence but then is exported or released from microsomes. The 34 N-terminal amino acids of the toxin fragment are sufficient to arrest translocation and prevent the microsomal accumulation of nascent chains that otherwise are sequestered into microsomes. These data support a role for the N-terminal region of PE37 in the translocation of the toxin from the endoplasmic reticulum to the cytosol in mammalian cells.
authors.affiliation: Laboratory of Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892.
authors.forename: C P
authors.initials: CP
authors.lastname: Theuer
authors.forename: J
authors.initials: J
authors.lastname: Buchner
authors.forename: D
authors.initials: D
authors.lastname: FitzGerald
authors.forename: I
authors.initials: I
authors.lastname: Pastan
mesh_terms: D036002:ADP Ribose Transferases; D000595:Amino Acid Sequence; D000818:Animals; D001427:Bacterial Toxins; D016923:Cell Death / Q000187:drug effects; D003600:Cytosol / Q000378:metabolism; D004285:Dogs; D004721:Endoplasmic Reticulum / Q000378:metabolism; D005098:Exotoxins / Q000235:genetics / Q000378:metabolism* / Q000633:toxicity*; D008861:Microsomes / Q000378:metabolism*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009842:Oligopeptides / Q000378:metabolism / Q000633:toxicity*; D010179:Pancreas / Q000378:metabolism; D010446:Peptide Fragments / Q000378:metabolism / Q000633:toxicity; D010957:Plasmids; D016133:Polymerase Chain Reaction / Q000379:methods; D014176:Protein Biosynthesis; D011550:Pseudomonas aeruginosa / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D015183:Restriction Mapping; D013698:Templates, Genetic; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A
chemical_list: D036002:ADP Ribose Transferases; D001427:Bacterial Toxins; D005098:Exotoxins; D009842:Oligopeptides; D010446:Peptide Fragments; D012333:RNA, Messenger; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A