干酪乳杆菌细菌素的抗菌机制分析

Antibacterial Mechanism of Bacteriocin from Lactobacillus casei

目的:分析和预测干酪乳杆菌细菌素基因及其编码蛋白的分子结构和理化性质,明确细菌素的抗菌机制。方法:利用生物信息学软件进行细菌素编码蛋白的结构预测和功能分析,采用氨基酸定点突变技术对预测的氨基酸位点进行点突变,检测突变体的抗菌活性。结果:干酪乳杆菌细菌素(LacA和LacB)属于热稳定、分泌信号肽的跨膜蛋白,LacA蛋白存在典型的抗菌结构域GxxxG,构建LacA蛋白中第40位V和第57位I的突变载体,两个位点中任何一个发生突变都明显影响细菌素的抗菌活性。结论:推测V40和I57是干酪乳杆菌细菌素发挥抑菌活性的关键氨基酸位点,为今后探索干酪乳杆菌细菌素(class IIb)抗菌机制提供理论依据。

Objective： This study aimed to analyze and predict the molecular structure and physicochemical properties of the bacteriocin gene and its encoded protein from Lactobacillus casei and to clarify the antibacterial mechanism of the bacteriocin. Methods： A variety of bioinformatics software were used to predict and analyze protein structure and function. Site-directed mutagenesis was applied to the predicted amino acid sites, and the antibacterial activities of the mutants were detected. Results： Bacteriocin from L. casei（Lac A and Lac B） was thermally stable, contained a secretory signal peptide and had a transmembrane region. Lac A contained a typical antimicrobial domain Gxxx G. The mutant vectors for V40 and I57 in Lac A were constructed, and the antimicrobial activity was significantly reduced when any of these two amino acids was mutated. Conclusion： V40 and I57 could be the key amino acid residues responsible for the antibacterial activity of L. casei. This study has provided a theoretical basis for exploring the antibacterial mechanism of bacteriocin from L. casei（class IIb）.