茎瘤固氮根瘤菌Azorhizobium caulinodans ORS571基因组分泌蛋白的生物信息学分析

Bioinformatics Analysis of Secreted Proteins in the Genome of Azorhizobium caulinodans ORS571

为了获取茎瘤固氮根瘤菌(Azorhizobium caulinodans ORS571)的分泌蛋白,以便更深入地了解该菌的共生固氮作用,本研究采用SignalP、TMHMM、PSORTb、TargetP、LipoP、TatP和SecretomeP软件对该菌全部4717个蛋白序列进行分析预测。结果共识别了653个分泌蛋白,其中具有分泌型信号肽的蛋白54个,具有RR-motif型信号肽的蛋白1个,具有脂蛋白信号肽的蛋白2个和非经典分泌蛋白596个。该菌含信号肽分泌蛋白仅占全部蛋白的1.2%,低于其它固氮菌。在分泌蛋白中识别了核酸内切酶和核糖核酸酶等6个核酸酶。它们可能参与宿主植物遗传物质的降解,干扰宿主遗传代谢,进一步在宿主植物侵染过程中起到重要作用。此外还识别了超氧化物歧化酶、过氧化氢酶和谷胱甘肽S-转移酶等4个抗氧化酶。它们可能参与活性氧的清除以保护固氮酶,是该菌固氮过程的重要参与者。

In order to identify secreted proteins in the genome ofAzorhizobium caulinodans ORS57 land get a better understanding of the mechanism of symbiotic nitrogen fixation, the 4 717 proteins sequence from the bacteria were analyzed and predicted with the use of SignalP, TMHMM, PSORTb, TargetP, LipoP, TatP and SecretomeP software. A total of 653 secreted proteins were identified. Among them, fifty-four proteins contained secretory signal peptides; one protein contained RR-motif signal peptide; two proteins contained lipoprotein signal peptides and 596 proteins contained non-classical secreted proteins. The percentage of the secreted proteins with signal peptides in all proteins was only 1.2%, which was lower than other nitrogen-fixing bacteria. Six nucleases such as endonuclease and ribonuclease were identified in these secreted proteins. They may involve in the degradation of the host plant genetic material, interfere with the metabolism of host genes, and further more play an important role in the host plant infection process. Moreover, four antioxidant enzymes were also identified, including superoxide dismutase, catalase and glutathione S-transferase. They may involve in the scavenging of active oxygen to protect nitrogenase, and are important participants in the process of nitrogen fixation of these bacteria.