title: Identification and characterization of CAMP cohemolysin as a potential virulence factor of Riemerella anatipestifer.
abstract: Riemerella anatipestifer is responsible for exudative septicemia in ducks. The genetic determinant of the CAMP cohemolysin, cam, from a strain of R. anatipestifer was cloned and expressed in Escherichia coli. Chromosomal DNA from serotype 19 strain 30/90 was used to construct a gene library in pBluescript II SK(-) vector in E. coli XL-1-Blue strain. The clones containing recombinant plasmids were screened for the CAMP reaction with Staphylococcus aureus. Those that showed cohemolysis were chosen for further analysis by sequencing. One of these clones, JFRA8, was subcloned to identify the smallest possible DNA fragment containing the CAMP cohemolysin determinant, which was located on a 3,566-bp BamHI-BstXI fragment which specified a 1,026-bp open reading frame. Clones containing recombinant plasmids carrying cam obtained by PCR cloning into E. coli M15 strain secreted an active CAMP cohemolysin. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blot analyses confirmed that the recombinant strain expressed a protein with a molecular mass of 37 kDa and that strains from serotypes 1, 2, 3, 5, 6, and 19 expressed the cohemolysin. The deduced amino acid sequence showed high homology to those of O-sialoglycoprotein endopeptidases. Hydrolysis of radioiodinated glycophorin A confirmed that Cam is a sialoglycoprotease.
authors.affiliation: Institute of Molecular Agrobiology, National University of Singapore, Singapore.
authors.forename: Karen C
authors.initials: KC
authors.lastname: Crasta
authors.forename: Kim-Lee
authors.initials: KL
authors.lastname: Chua
authors.forename: Sumathi
authors.initials: S
authors.lastname: Subramaniam
authors.forename: Joachim
authors.initials: J
authors.lastname: Frey
authors.forename: Hilda
authors.initials: H
authors.lastname: Loh
authors.forename: Hai-Meng
authors.initials: HM
authors.lastname: Tan
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics* / Q000302:isolation & purification; D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000032:analysis; D010450:Endopeptidases / Q000378:metabolism; D005417:Flavobacterium / Q000737:chemistry / Q000235:genetics*; D005784:Gene Amplification; D015870:Gene Expression; D016680:Genome, Bacterial; D006460:Hemolysin Proteins / Q000235:genetics* / Q000302:isolation & purification; D007118:Immunoassay; D008969:Molecular Sequence Data; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D014774:Virulence
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D006460:Hemolysin Proteins; D010450:Endopeptidases