title: Localization and functional analysis of PepI, the immunity peptide of Pep5-producing Staphylococcus epidermidis strain 5.
abstract: Pep5 is a cationic pore-forming lantibiotic produced by Staphylococcus epidermidis strain 5. The producer strain protects itself from the lethal action of its own bacteriocin through the 69-amino-acid immunity peptide PepI. The N-terminal segment of PepI contains a 20-amino-acid stretch of apolar residues, whereas the C terminus is very hydrophilic, with a net positive charge. We used green fluorescent protein (GFP)-PepI fusions to obtain information on its localization in vivo. PepI was found to occur outside the cytoplasm and to accumulate at the membrane-cell wall interface. The extracellular localization appeared essential for conferring immunity. We analyzed the functional role of the specific segments by constructing various mutant peptides, which were also fused to GFP. When the hydrophobic N-terminal segment of PepI was disrupted by introducing charged amino acids, the export of PepI was blocked and clones expressing such mutant peptides were Pep5 sensitive. When PepI was successively shortened at the C terminus, in contrast, its export properties remained unchanged whereas its ability to confer immunity was gradually reduced. The results show that the N-terminal part is required for the transport of PepI and that the C-terminal part is important for conferring the immunity phenotype. A concept based on target shielding is proposed for the PepI immunity mechanism.
authors.affiliation: Institut für Medizinische Mikrobiologie und Immunologie, Universität Bonn, D-53105 Bonn, Germany.
authors.forename: Anja
authors.initials: A
authors.lastname: Hoffmann
authors.forename: Tanja
authors.initials: T
authors.lastname: Schneider
authors.forename: Ulrike
authors.initials: U
authors.lastname: Pag
authors.forename: Hans-Georg
authors.initials: HG
authors.lastname: Sahl
mesh_terms: D000595:Amino Acid Sequence; D000626:Aminopeptidases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001430:Bacteriocins; D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism; D002473:Cell Wall / Q000378:metabolism; D024881:Drug Resistance, Bacterial; D015964:Gene Expression Regulation, Bacterial; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D009154:Mutation; D010455:Peptides / Q000378:metabolism* / Q000494:pharmacology; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D013212:Staphylococcus epidermidis / Q000187:drug effects* / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D001430:Bacteriocins; D008164:Luminescent Proteins; D010455:Peptides; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; C054222:lantibiotic Pep5; D000626:Aminopeptidases; C022450:prolyl aminopeptidase