title: Characterization, kinetics, and possible function of Kazal-type proteinase inhibitors of Chinese white shrimp, Fenneropenaeus chinensis.
abstract: Serine proteinase inhibitor plays an essential role in arthropods by restraining the activities of endogenic or exogenic serine proteinases. Four Kazal-type serine proteinase inhibitors, Fcspi-1-4, from the hepatopancreas of Chinese white shrimp, Fenneropenaeus chinensis, were cloned and identified. The open reading frames (ORFs) of Fcspis are 1389, 1236, 1080, and 939 base pairs, encode the pre-proteins of 462, 411, 359, and 312 amino acids and form the 9, 8, 7, and 6 typical Kazal domains, respectively. When analyzing the amino acid sequences of the four inhibitors, it was found that they might have been derived from the same transcript, which was subjected to alternative splicing, and none of the Kazal domains were identical within each inhibitor. Multiple alignments showed that the Kazal inhibitors were homologous with a conserved motif of Cx(3)Cx(6)VCGSDGxTYx(3)CxLx(5)Cx(5)ITx(6)GC. The results from RT-PCR indicated that the expression of Fcspis as a whole was upregulated by bacterial challenge, no obvious change was noticed after viral challenge, and Fcspi-1 had a similar expression pattern with that of Fcspis. Recombinant FcSPIs were successfully expressed in bacteria and purified for further study. Recombinant FcSPI-1 was sensitive to DTT and had thermal stability. The inhibitory kinetics assay suggested that rFcSPI-1 was a mixed-type fast tight binding inhibitor with inhibitory activities against subtilisin A at a molar ratio of 1:1, 1:2 against proteinase K, and 2:1 against elastase. It can firmly bound to two Gram-positive and one Gram-negative bacteria but without anti-bacterial ability. In addition, it inhibited the activities of both bacterial-secreted proteinases and natural chymotrypsin of Chinese white shrimp, suggesting that FcSPI-1 may participate in the immune defence response by inhibition of bacterial pathogen proteinases and possibly be involved in the regulation of shrimp proteinase activity.
authors.affiliation: School of Life Sciences, Shandong University, Jinan 250100, China.
authors.forename: Zong-Heng
authors.initials: ZH
authors.lastname: Wang
authors.forename: Xiao-Fan
authors.initials: XF
authors.lastname: Zhao
authors.forename: Jin-Xing
authors.initials: JX
authors.lastname: Wang
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D006090:Gram-Negative Bacteria / Q000201:enzymology; D006094:Gram-Positive Bacteria / Q000201:enzymology; D043143:Hepatopancreas / Q000378:metabolism*; D015151:Immunoblotting / Q000662:veterinary; D007700:Kinetics; D008969:Molecular Sequence Data; D033561:Penaeidae / Q000276:immunology / Q000378:metabolism*; D012313:RNA / Q000737:chemistry / Q000235:genetics; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000235:genetics / Q000302:isolation & purification / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000662:veterinary; D016415:Sequence Alignment; D012697:Serine Endopeptidases / Q000378:metabolism*; D015842:Serine Proteinase Inhibitors / Q000096:biosynthesis* / Q000235:genetics / Q000302:isolation & purification / Q000494:pharmacology
chemical_list: D011994:Recombinant Proteins; D015842:Serine Proteinase Inhibitors; D012313:RNA; D012697:Serine Endopeptidases