title: N-tail translocation of mature beta-lactamase across the Escherichia coli cytoplasmic membrane.
abstract: Mature beta-lactamase was attached to the N-terminus of human glycophorin C, an N-out membrane protein lacking a cleavable signal peptide (an N-tail membrane protein). When synthesised in Escherichia coli more than 30% of the intact mature beta-lactamase-glycophorin C molecules assembled N-out, C-in into the cytoplasmic membrane. The N-tail translocated beta-lactamase folded into an enzymatically active form, but it was more susceptible to proteolysis than the equivalent portion of beta-lactamase-glycophorin C synthesised with an N-terminal signal peptide. Its translocation was virtually abolished when the N-out domain of glycophorin C was truncated or when the basic residues C-terminally flanking the glycophorin C membrane-spanning segment were replaced with neutral ones.
authors.affiliation: Biochemistry Group, School of Biological Sciences, University of Sussex, Falmer, Brighton, UK.
authors.forename: C
authors.initials: C
authors.lastname: Mitsopoulos
authors.forename: L
authors.initials: L
authors.lastname: Hashemzadeh-Bonehi
authors.forename: J K
authors.initials: JK
authors.lastname: Broome-Smith
mesh_terms: D001692:Biological Transport; D002462:Cell Membrane / Q000201:enzymology; D019286:Endopeptidase K; D004926:Escherichia coli / Q000201:enzymology*; D006021:Glycophorins / Q000737:chemistry* / Q000235:genetics; D006801:Humans; D017510:Protein Folding; D021382:Protein Sorting Signals / Q000502:physiology; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D001618:beta-Lactamases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D006021:Glycophorins; D021382:Protein Sorting Signals; D011993:Recombinant Fusion Proteins; D019286:Endopeptidase K; D001618:beta-Lactamases