title: Peptidoglycan degradation by specialized lytic transglycosylases associated with type III and type IV secretion systems.
abstract: Specialized lytic transglycosylases are muramidases capable of locally degrading the peptidoglycan meshwork of Gram-negative bacteria. Specialized lytic transglycosylase genes are present in clusters encoding diverse macromolecular transport systems. This paper reports the analysis of selected members of the specialized lytic transglycosylase family from type III and type IV secretion systems. These proteins were analysed in vivo by assaying their ability to complement the DNA transfer defect of the conjugative F-like plasmid R1-16 lacking a functional P19 protein, the specialized lytic transglycosylase of this type IV secretion system. Heterologous complementation was accomplished using IpgF from the plasmid-encoded type III secretion system of Shigella sonnei and TrbN from the type IV secretion system of the conjugative plasmid RP4. In contrast, neither VirB1 proteins (Agrobacterium tumefaciens, Brucella suis) nor IagB (Salmonella enterica) could functionally replace P19. In vitro, IpgF, IagB, both VirB1 proteins, HP0523 (Helicobacter pylori) and P19 displayed peptidoglycanase activity in zymogram analyses. Using an established test system and a newly developed assay it was shown that IpgF degraded peptidoglycan in solution. IpgF was active only after removal of the chaperonin GroEL, which co-purified with IpgF and inhibited its enzymic activity. A mutant IpgF protein in which the predicted catalytic amino acid, Glu42, was replaced by Gln, was completely inactive. IpgF-catalysed peptidoglycan degradation was optimal at pH 6 and was inhibited by the lytic transglycosylase inhibitors hexa-N-acetylchitohexaose and bulgecin A.
authors.affiliation: Institut für Molekulare Biowissenschaften (IMB), Karl-Franzens-Universität Graz, Universitätsplatz 2, A-8010 Graz, Austria.
authors.forename: Doris
authors.initials: D
authors.lastname: Zahrl
authors.affiliation: Institut für Molekulare Biowissenschaften (IMB), Karl-Franzens-Universität Graz, Universitätsplatz 2, A-8010 Graz, Austria.
authors.forename: Maria
authors.initials: M
authors.lastname: Wagner
authors.affiliation: Institut für Molekulare Biowissenschaften (IMB), Karl-Franzens-Universität Graz, Universitätsplatz 2, A-8010 Graz, Austria.
authors.forename: Karin
authors.initials: K
authors.lastname: Bischof
authors.affiliation: Institut für Molekulare Biowissenschaften (IMB), Karl-Franzens-Universität Graz, Universitätsplatz 2, A-8010 Graz, Austria.
authors.forename: Michaela
authors.initials: M
authors.lastname: Bayer
authors.affiliation: Institut für Molekulare Biowissenschaften (IMB), Karl-Franzens-Universität Graz, Universitätsplatz 2, A-8010 Graz, Austria.
authors.forename: Barbara
authors.initials: B
authors.lastname: Zavecz
authors.affiliation: Institut für Molekulare Biowissenschaften (IMB), Karl-Franzens-Universität Graz, Universitätsplatz 2, A-8010 Graz, Austria.
authors.forename: Andreas
authors.initials: A
authors.lastname: Beranek
authors.affiliation: Institut für Molekulare Biowissenschaften (IMB), Karl-Franzens-Universität Graz, Universitätsplatz 2, A-8010 Graz, Austria.
authors.forename: Christoph
authors.initials: C
authors.lastname: Ruckenstuhl
authors.affiliation: Institut für Molekulare Biowissenschaften (IMB), Karl-Franzens-Universität Graz, Universitätsplatz 2, A-8010 Graz, Austria.
authors.forename: Gernot E
authors.initials: GE
authors.lastname: Zarfel
authors.affiliation: Institut für Molekulare Biowissenschaften (IMB), Karl-Franzens-Universität Graz, Universitätsplatz 2, A-8010 Graz, Austria.
authors.forename: Günther
authors.initials: G
authors.lastname: Koraimann
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D002232:Carbocyanines / Q000378:metabolism; D003227:Conjugation, Genetic; D005456:Fluorescent Dyes / Q000378:metabolism; D005816:Genetic Complementation Test; D016695:Glycosyltransferases / Q000378:metabolism*; D006090:Gram-Negative Bacteria / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D009113:Muramidase / Q000378:metabolism; D009154:Mutation; D010457:Peptidoglycan / Q000378:metabolism*; D021381:Protein Transport
chemical_list: D001426:Bacterial Proteins; D002232:Carbocyanines; D005456:Fluorescent Dyes; D010457:Peptidoglycan; C089187:cyanine dye 3; D016695:Glycosyltransferases; D009113:Muramidase