title: Molecular characterization of the cathepsin B of turbot (Scophthalmus maximus).
abstract: Cathepsin B is an enzymatic protein belonging to the peptidase C1 family. It is involved in diverse physiological and pathological functions that include immune response. In this study, we identified and characterized a cathepsin B homolog (SmCatB) from turbot (Scophthalmus maximus). SmCatB is composed of 330 amino acid residues and possesses typical domain architecture of cathepsin B, which contains a propeptide region and a cysteine protease domain, and the latter processes four conserved residues (Q101, C107, H277, and N297) in the active site. SmCatB shares 80.6-87.6% overall sequence identities with the cathepsin B of a number of teleost. SmCatB expression was detected in a wide range of tissues and upregulated by bacterial infection in a time-dependent manner. Recombinant SmCatB (rSmCatB-WT) purified from Escherichia coli exhibited apparent protease activity, which was optimal at 50 °C and pH 5.5. Compared to rSmCatB-WT, the mutant proteins rSmCatB-C107S, rSmCatB-H277A, and rSmCatB-N297A, which bear C107S, H277A, and N297A mutations, respectively, were significantly reduced in protease activity, with the highest reduction observed with rSmCatB-N297A. These results indicate that SmCatB is a bioactive protease that depends on the conserved structural features and that SmCatB is involved in pathogen-induced immune response.
authors.affiliation: Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, 266071, China.
authors.forename: Ze-jun
authors.initials: ZJ
authors.lastname: Zhou
authors.forename: Reng
authors.initials: R
authors.lastname: Qiu
authors.forename: Jian
authors.initials: J
authors.lastname: Zhang
mesh_terms: D000595:Amino Acid Sequence; D000704:Analysis of Variance; D000818:Animals; D001483:Base Sequence; D002401:Cathepsin B / Q000235:genetics* / Q000378:metabolism*; D003001:Cloning, Molecular; D017931:DNA Primers / Q000235:genetics; D004926:Escherichia coli; D005412:Flatfishes / Q000235:genetics* / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D059748:Proteolysis / Q000187:drug effects; D060888:Real-Time Polymerase Chain Reaction / Q000662:veterinary; D011994:Recombinant Proteins / Q000378:metabolism* / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000662:veterinary; D017422:Sequence Analysis, DNA / Q000662:veterinary; D017385:Sequence Homology; D013696:Temperature
chemical_list: D017931:DNA Primers; D011994:Recombinant Proteins; D002401:Cathepsin B