AiiA蛋白的可溶性表达及其抗菌活性研究

SOLUBLE EXPRESSION OF AlIA PROTEIN AND ANALYSIS OF ITS ANTIMICROBIAL ACTIVITY

AHLs是革兰氏阴性细菌在增殖过程中产生的一类信号分子,与其致病性密切相关。AiiA蛋白作为一种胞内解酯酶。能水解致病菌产生的AHLs分子,使内酯环开环后不能再激活某些胞外酶的表达,从而极大地减弱了细菌的致病性。本研究从苏云金芽孢杆菌LLB15中分离编码aiiA基因的质粒DNA,用PCR方法克隆AiiA基因,并利用pET载体构建6-His融合表达质粒pET29a-aiiA,转化E.coli BL21(DE3)菌株,并筛选得到E.coli BL21(DE3)-pET29a-aiiA工程菌。在20℃的低温和0.8 mmol/L IPTG条件下,经25 h的诱导表达,获得了54.4μg/mL可溶性AiiA蛋白。通过镍柱亲和层析,在国内外首次纯化了带6-His标记的AiiA蛋白。水解活性和抗病性检测表明。该蛋白能水解AHLs分子。对胡萝卜欧文氏软腐病菌具有较强的抗病作用。

AHLs are signaling molecules produced by Gram-negative bacterium during their proliferation. These molecules are closely related with bacteria pathogenicity. Alia protein, functioning as a intracellular lactonase, hydrolyses AHLs at lactone loop in the molecule to reduce its biological activity and also dramatically reduces pathogenicity of bacterium at the same time. In this study, DNA fragment encoding aiiA gene was amplified from the plasmid derived from Bacillus thuringiensis by PCR. Expression vector, pET29a-aiiA, was constructed and transformed into bacteria strain of E.coli BL21 （DE3） for expression of AiiA protein. After 25h induction with 0.8 mmol/ L IPTG at 20℃, the protein AliA expressed in soluble form by recombinant strain reached about 54.4 ug/mL. The recombinant protein was purified with Ni-affinity chromatography. Biological activity analysis showed that AiiA protein had a capability to hydrolyse AHLs, and strong antimicrobial activity for Eriwinia carotovora.