利用PCR方法从黏质沙雷氏菌(Serratia marcescens)C8-8中克隆到编码几丁质酶的chiA基因,大小为1692bp,推测其编码一条长563个氨基酸的多肽链,分子量约为60900.同源分析研究结果表明从C8-8中克隆的chiA基因序列与黏质沙雷氏菌株141(DQ990373.1)和14041菌株(DQ493896.1)的chiA基因序列相似性最高,达到99％.结构域分析结果表明从C8-8中克隆的chiA基因N末端(23AA)存在典型的信号肽序列,C端存在另外两个结构域,即PKD区(73AA)和几丁质酶催化区(387AA).采用大肠杆菌表达系统重组表达chiA基因,结果表明重组菌株在几丁质诱导培养基上能产生透明的水解圈.采用SDS-PAGE电泳分析,结果表明chiA重组表达产物的相对分子质量约为60000,与预测分子量大小基本一致.初步提纯后,生物活性试验结果表明该重组表达产物能水解几丁质,在几丁质培养基上产生透明的水解圈.%An open reading frame encoding chiA gene was cloned from the Serratia marcescens strain C8-8 genomic DNA by PCR, with the length of 1 692 bp. Its sequence was 99% identical with chiA sequences of Serratia marcescens 141 and 14041. Domain analysis showed that the cloned chiA gene involved a typical signal peptide sequence at N-terraination (23 AA), and PKD domain (73 AA) and chitinase catalytic domain (387 AA) at C-termination. The PCR fragment was digested and cloned into plasmid pET28a to construct plasmid pET28a-ChiA, which was then transformed into expression host Escherichia. coli DH3. The recombined strain DH3 ChiA could yield transparent hydrolyzed zone on the colloidal chi-tin plate induced by isopropyl-1 -thiogalactopyranoside (IPTG). A protein with molecular weight about 60 000 was expressed by DH3 ChiA, and could also yield a hydrolyzed rone on the colloidal chitin plate. It indicated that chiA gene from C8-8 could be utilized as a potential biological factor for control of fungi.
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