title: Mutational analysis of the zinc metalloprotease EmpA of Vibrio anguillarum.
abstract: The extracellular zinc metalloprotease, EmpA, is a putative virulence factor involved in pathogenicity of the fish pathogen Vibrio anguillarum. The 611-amino acid precursor of this enzyme is encoded by the empA gene. The residues His346, His350, Glu370, Glu347, His429, Tyr361 and Asp417 are highly conserved and putatively function together at the active site of the enzyme. In this study, empA was inserted into pET24d(+) and expressed in Escherichia coli strain BL21(DE3) as a 6 x His tagged protein (r-EmpA). All the conserved residues of EmpA mentioned above were individually mutated by site-directed mutagenesis and the mutants were also expressed (m-r-EmpAs). r-EmpA and m-r-EmpAs were purified, and assayed for their proteolytic activities with azocasein as the substrate and cytotoxicities on a flounder gill cell line. m-r-EmpAs that had been mutated at His346, His350, Glu370 and Glu347 almost completely lost their proteolytic activity and cytotoxicity, pointing towards the essential roles played by these residues. In contrast, those mutated at Tyr361, His429 and Asp417 still retained a partial proteolytic activity and cytotoxicity. Our results indicate that these conserved residues play important roles in enzymatic activity and that the proteolytic activity of the enzyme is involved in the pathogenesis of V. anguillarum
authors.affiliation: Department of Marine Biology, College of Marine Life Sciences, Ocean Univesity of China, P.R.China.
authors.forename: Hui
authors.initials: H
authors.lastname: Yang
authors.forename: Jixiang
authors.initials: J
authors.lastname: Chen
authors.forename: Guanpin
authors.initials: G
authors.lastname: Yang
authors.forename: Xiao-Hua
authors.initials: XH
authors.lastname: Zhang
authors.forename: Yun
authors.initials: Y
authors.lastname: Li
mesh_terms: D019943:Amino Acid Substitution / Q000235:genetics; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism* / Q000633:toxicity; D002364:Caseins / Q000378:metabolism; D002460:Cell Line; D003001:Cloning, Molecular; D017124:Conserved Sequence; D004252:DNA Mutational Analysis; D004926:Escherichia coli / Q000235:genetics; D005432:Flounder; D015870:Gene Expression; D045726:Metalloproteases / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism* / Q000633:toxicity; D016297:Mutagenesis, Site-Directed; D020125:Mutation, Missense; D014733:Vibrio / Q000201:enzymology* / Q000235:genetics / Q000472:pathogenicity
chemical_list: D001426:Bacterial Proteins; D002364:Caseins; C026018:azocasein; C500552:EmpA protein, Vibrio anguillarum; D045726:Metalloproteases