黏质沙雷氏菌plaA及plaS的生物信息学分析

Bioinformatics analysis of plaA and plaS in Serratia marcescens

磷脂酶A1是一类水解磷脂的酶类,利用生物信息学方法对磷脂酶A1基因及辅助蛋白基因进行分析,为进一步研究磷脂酶提供基础。通过对黏质沙雷氏菌plaA(Phospholipase A1)及plaS(accessory protein)进行克隆和测序,对其核苷酸序列和氨基酸序列特征进行分析;对其蛋白质二级结构、三级结构进行了预测;同时运用ML、MP和BI 3种方法构建了系统发育树。结果表明,plaS的dN/dS的值较plaA高,所受的选择压力较小,进化速率较快;Pla A蛋白和Pla S蛋白的二级结构都以α螺旋和无规则卷曲为主;plaA与plaS联合构建的系统发育树支持率较16S单独构建的支持率高。基于plaA、plaS和16S 3个基因联合构建的系统发育树中,解脲沙雷氏菌和嗜线虫沙雷氏菌都与黏质沙雷氏菌聚为一支,在亲缘关系上,这两种沙雷氏菌可能跟黏质沙雷氏菌更为接近。

Phospholipase A1(plaA)is an enzyme that hydrolyzes phospholipids.We used bioinformatics methods to analyze plaA and its accessory protein gene(plaS),which will provide a basis for further study of phospholipase.We cloned and sequenced the plaA and plaS of Serratia marcescens,and the characteristics of nucleotide and amino acid sequence were analysed.Furthermore,we also predicted the secondary structure and tertiary structure of PlaA and PlaS protein.Phylogenetic trees were reconstructed using maximum parsimony(MP),maximum likelihood(ML)and bayesian inference(BI)methods.The results showed that the dN/dS of plaS was higher than that of plaA,suggesting that the selection pressure is stronger and the evolution rate is slower.The secondary structure of PlaA and PlaS protein were mainly composed ofαhelix and random coil.Bootstrap values of16S tree were lower than that of trees referred from two genes(plaA+plaS).Based on the phylogenetic tree which constructed by plaA,plaS and16S,both Serratia nematodiphila and S.ureilytica were clustered together with S.marcescens.The two strains of Serratia may be more related to S.marcescens.