title: Expression characterization and activity analysis of a cathepsin B from Pacific abalone Haliotis discus hannai.
abstract: Cathepsin B (EC 3.4.22.1) is a member of lysosomal cysteine protease and has a papain-like fold. In mammals, it is involved in protein degradation and other physiological processes including immune response. However, little is known about the function of cathepsin B in mollusks. In this study, we identified and analyzed a cathepsin B homolog (HdCatB) from Pacific abalone (Haliotis discus hannai), an economically important mollusk species cultured in East Asia. HdCatB is composed of 336 amino acid residues and its mature form is predicted to start at residue 86. HdCatB possesses typical domain architecture of cathepsin B and contains a propeptide region and a cysteine protease domain, the latter containing the four active site residues (Q108, C114, H282, and N302) that are conserved in many different organisms. HdCatB shares 40-60% overall sequence identities with the cathepsin Bofa number of vertebrates and invertebrates and is phylogenetically very close to mollusk cathepsin B. Quantitative real time RT-PCR analysis revealed that HdCatB expression occurred in multiple tissues and was upregulated by bacterial infection. Recombinant HdCatB purified from Escherichia coli exhibited apparent protease activity, which was optimal at 45 °C and pH 6.0. These results indicate that HdCatB is a bioactive protease that is likely to be implicated in the immune response of abalone during bacterial infection.
authors.affiliation: Institute of Oceanology, Chinese Academy of Sciences, 7 Nanhai Road, Qingdao 266071, China.
authors.forename: Reng
authors.initials: R
authors.lastname: Qiu
authors.forename: Xiao
authors.initials: X
authors.lastname: Liu
authors.forename: Yong-hua
authors.initials: YH
authors.lastname: Hu
authors.forename: Bo-guang
authors.initials: BG
authors.lastname: Sun
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002401:Cathepsin B / Q000737:chemistry / Q000235:genetics* / Q000276:immunology* / Q000378:metabolism; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000032:analysis; D004926:Escherichia coli / Q000235:genetics; D049851:Gastropoda / Q000235:genetics* / Q000276:immunology* / Q000378:metabolism; D005786:Gene Expression Regulation; D007273:Injections, Intramuscular / Q000662:veterinary; D008969:Molecular Sequence Data; D009928:Organ Specificity; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000032:analysis; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D014733:Vibrio / Q000502:physiology
chemical_list: D018076:DNA, Complementary; D012333:RNA, Messenger; D011994:Recombinant Proteins; D002401:Cathepsin B