title: Characterisation of an extracellular vibriolysin of the fish pathogen Moritella viscosa.
abstract: Moritella viscosa causes winter ulcer disease in salmonids. The aim of the present work was to isolate and partially characterise an extracellular peptidase from M. viscosa, and to study its role in virulence. The peptidase, termed MvP1, was a 38-kDa metallopeptidase produced in late exponential growth. The optimum temperature for MvP1 was 40 degrees C, but the enzyme was active over a broad range of temperatures. MvP1 was non-lethal to salmon at concentrations up to 0.22microg/g fish, but extracellular products were lethal to salmon. MvP1 degraded casein, gelatin and collagen from lumpfish skin. It caused considerable tissue necrosis and hemorrhages at the site of injection, and affected cell-cell adhesions in EPC and BF-2 cell lines, but was not highly cytotoxic. The peptidase partially degraded fish IgM heavy chain but was non-hemolytic. The mvp1 gene was sequenced and encoded a 734-aa polypeptide containing a signal sequence, an N-terminal propeptide, a mature peptidase domain and a C-terminal propeptide. The MvP1 propeptide undergoes both N-terminal and C-terminal processing and different C-terminal processing results in the formation of several active isoforms of the mature peptidase. The catalytic domain showed highest sequence similarity with several vibriolysins (EC 3.4.24.25) originating from Pseudoalteromonas strains, showing up to 80% aa identity. The results indicate that MvP1 is a previously unknown vibriolysin that might affect M. viscosa virulence by aiding in the invasion and dissemination of the bacterium in its host, by causing tissue destruction.
authors.affiliation: Institute for Experimental Pathology, University of Iceland, Keldur, Vesturlandsvegi, 112 Reykjavik, Iceland.
authors.forename: Bryndis
authors.initials: B
authors.lastname: Bjornsdottir
authors.forename: Olafur H
authors.initials: OH
authors.lastname: Fridjonsson
authors.forename: Steinunn
authors.initials: S
authors.lastname: Magnusdottir
authors.forename: Valgerdur
authors.initials: V
authors.lastname: Andresdottir
authors.forename: Gudmundur O
authors.initials: GO
authors.lastname: Hreggvidsson
authors.forename: Bjarnheidur K
authors.initials: BK
authors.lastname: Gudmundsdottir
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015180:Electrophoresis, Gel, Two-Dimensional / Q000662:veterinary; D005393:Fish Diseases / Q000382:microbiology*; D016905:Gram-Negative Bacterial Infections / Q000382:microbiology / Q000662:veterinary*; D007075:Immunoglobulin M / Q000378:metabolism; D007527:Isoenzymes / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D008666:Metalloendopeptidases / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D008969:Molecular Sequence Data; D034221:Moritella / Q000201:enzymology* / Q000235:genetics / Q000302:isolation & purification; D012487:Salmonidae; D037521:Virulence Factors / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism
chemical_list: D007075:Immunoglobulin M; D007527:Isoenzymes; D037521:Virulence Factors; D008666:Metalloendopeptidases