title: Membrane localisation of a UDP-sugar hydrolase, in Salmonella, is by an uncleaved N-terminal signal peptide.
abstract: Most isolates of Salmonella contain two unrelated UDP-sugar hydrolases, one of which, encoded by the ushB gene, is inner membrane-associated. Previous studies showed that this enzyme contains a typical N-terminal signal peptide; the evidence also indicated, however, that this peptide is not cleaved, and serves to anchor the UshB protein in the inner membrane. In this report, we present strong evidence that this is indeed the case by using ushB'-'blaM fusions to demonstrate that this signal peptide is capable of localising beta-lactamase to the inner membrane. We also present evidence that UshB is located on the exterior (periplasmic) side of the membrane, and hence has an 'N-terminus inside/C-terminus outside' membrane orientation, consistent with a role in the degradation of external substrates.
authors.affiliation: Faculty of Science and Technology, Griffith University, Brisbane, Queensland, Australia.
authors.forename: R A
authors.initials: RA
authors.lastname: Jones
authors.forename: D M
authors.initials: DM
authors.lastname: Burns
authors.forename: D J
authors.initials: DJ
authors.lastname: Carruthers
authors.forename: I R
authors.initials: IR
authors.lastname: Beacham
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D006867:Hydrolases / Q000235:genetics / Q000302:isolation & purification*; D008565:Membrane Proteins / Q000235:genetics / Q000302:isolation & purification*; D008969:Molecular Sequence Data; D021382:Protein Sorting Signals; D012475:Salmonella / Q000201:enzymology*; D014539:Uridine Diphosphate Sugars; D001618:beta-Lactamases / Q000302:isolation & purification
chemical_list: D008565:Membrane Proteins; D021382:Protein Sorting Signals; D014539:Uridine Diphosphate Sugars; D006867:Hydrolases; D001618:beta-Lactamases