| Summary: | 碩士 === 國立中山大學 === 生物科學系研究所 === 96 === Immunoglobulin A (IgA), a major serum immunoglobulin and a predominant antibody in the external secretions that bathe mucosal surfaces, plays key roles in immune protection. Some pathogenic bacteria including Haemophilus influenzae and Neisseria meningitides, however, produce a protease called IgA1 protease to impair the function of IgA1. The iga mRNA is initially translated into a large precursor containing four distinct domains: a 31-amino acid signal peptide which leads the precursor to the periplasmic space, an 105-kDa protease domain which cleaves host IgA1 molecule, a β-domain responsible for autotransportation of the protease domain, and a linker α-protein between the protease and the β-domain. The hydrolytic function of the protease and the role of the β-core had been studied extensively, but the role of the α-protein has never been studied. Thus this study is designed to reveal the possible functions of α-protein in the proliferation of lymphocytes. To complete the project, PCR was used to amplify the DNA fragment for α-protein using iga gene (Gene Bank DQ683357) as template. The fragment spans nucleotide numbers of 1015-1405. The fragment was then cloned into pGEX-2T for expression. Recombinant α-protein was purified using glutathione -Sepharose column. The purified recombinant protein did not seem to affect the cell growth at the concentration of 1 μg/ml compared with the medium control or GST control. Interestingly, when the concentration was increased to 5 μg/ml or 10 μg/ml, α-protein seems to enhance the cell growth on the 2nd, 4th and 6th day assays, The results suggested that α-protein may enhance the cell growth in 4 days.
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