title: Characterization and localization of the KpsE protein of Escherichia coli K5, which is involved in polysaccharide export.
abstract: In Escherichia coli with group II capsules, the synthesis and cellular expression of capsular polysaccharide are encoded by the kps gene cluster. This gene cluster is composed of three regions. The central region 2 encodes proteins involved in polysaccharide synthesis, and the flanking regions 1 and 3 direct the translocation of the finished polysaccharide across the cytoplasmic membrane and its surface expression. The kps genes of the K5 polysaccharide, which is a group II capsular polysaccharide, have been cloned and sequenced. Region 1 contains the kpsE, -D, -U, -C, and -S genes. In this communication we describe the KpsE protein, the product of the kpsE gene. A truncated kpsE gene was fused with a truncated beta-galactosidase gene to generate a fusion protein containing the first 375 amino acids of beta-galactosidase and amino acids 67 to 382 of KpsE (KpsE'). This fusion protein was isolated and cleaved with factor Xa, and the purified KpsE' was used to immunize rabbits. Intact KpsE was extracted from the membranes of a KpsE-overexpressing recombinant strain with octyl-beta-glucoside. It was purified by affinity chromatography with immobilized anti-KpsE antibodies. Cytofluorometric analysis using the anti-KpsE antibodies with whole cells and spheroplasts, as well as sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blotting (immunoblotting) of proteins from spheroplasts and membranes before and after treatment with proteinase K, indicated that the KpsE protein is associated with the cytoplasmic membrane and has an exposed periplasmic domain. By TnphoA mutagenesis and by constructing beta-lactamase fusions to the KpseE protein, it was possible to determine the topology of the KpsE protein within the cytoplasmic membrane.
authors.affiliation: Max-Planck-Institut für Immunobiologie, Freiburg, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Rosenow
authors.forename: F
authors.initials: F
authors.lastname: Esumeh
authors.forename: I S
authors.initials: IS
authors.lastname: Roberts
authors.forename: K
authors.initials: K
authors.lastname: Jann
mesh_terms: D000595:Amino Acid Sequence; D016667:Bacterial Capsules / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification*; D015153:Blotting, Western; D002462:Cell Membrane / Q000737:chemistry*; D004926:Escherichia coli / Q000737:chemistry* / Q000235:genetics; D029968:Escherichia coli Proteins; D008565:Membrane Proteins / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification*; D026901:Membrane Transport Proteins; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D011135:Polysaccharides, Bacterial / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000276:immunology; D017421:Sequence Analysis; D013347:Subcellular Fractions / Q000737:chemistry / Q000276:immunology
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D011135:Polysaccharides, Bacterial; D011993:Recombinant Fusion Proteins; C084729:kpsE protein, E coli