酿酒酵母分泌蛋白组的计算机分析

 结合计算机技术和生物信息学的方法，采用组合的信号肽分析软件SignalP v3.0、TargetP v1.01、Big-PI predictor和TMHMM v2.0对已公布的6 700个酿酒酵母（Saccaromyces cerevieiae）基因的N-端氨基酸序列进行信号肽分析，同时系统分析了信号肽的类型及结构。结果表明，在6 700个酿酒酵母蛋白中，163个为Sec-信号肽分泌蛋白，经Sec途径分泌。在163个分泌蛋白中，有47个的信号肽没有典型的N-区，仅有H-区和C-区，其余116个分泌蛋白的信号肽包含完整的3个区，即N-区、H-区和C-区。比较了酿酒酵母与白假丝酵母菌(Candida albicans)分泌蛋白信号肽的氨基酸组成顺序，表明酿酒酵母与白假丝酵母菌的信号肽的氨基酸组成和顺序差异很大，两者信号肽长度分布范围、氨基酸种类及其出现频率大体一致。在酿酒酵母分泌蛋白中出现了少数氨基酸组成完全一致的信号肽，为进一步确认具有相同信号肽的分泌蛋白是否具有同源性，分别采用BLAST 2 SEQUENECES 和CLUSTAL W 对具有相同信号肽的分泌蛋白进行了序列比对。结果表明具有相同信号肽的分泌蛋白同源性非常高，氨基酸组成也非常保守。由此可以推断，编码这些分泌蛋白的基因属于旁系同源基因（paralogous）。酿酒酵母作为一种模式生物，以其诸多的优点，被认为是表达真核外源蛋白的首选宿主。对酿酒酵母进行基因组水平的分泌蛋白及信号肽结构的分析，可更好地利用该宿主表达分泌型的外源蛋白研究提供参考信息。

Computational Analysis of Signal Peptide-Dependent Secreted Proteins in Saccaromyces cerevisiae

The internet-based software such as the SignalP v3.0, TargetP v1.01, Big-PI predictor and TMHMM v2.0 were combined to predict the signal peptides, and the signal peptide-dependent secreted proteins among the 6700 ORFs in Saccharomyces cerevisiae genome. The results showed that 163 proteins were the secreted ones containing signal peptides among 6700 proteins, and they were secreted via Sec pathway. Among the 163 secreted proteins, the signal peptides of 47 secreted proteins only comprised by H-domain and C-domain, without N-domain, but the signal peptides of other 116 secreted proteins including the complete three domains. There were differences on constitution of signal peptides between the secreted proteins of Saccharomyces cerevisiae and ones of Candida albicans, but the length and amino acids types of their signal peptides were similar in general. There were few of the same signal peptides occurred in the secreted proteins of Saccharomyces cerevisiae genome, in order to compare the homology among the secreted proteins with the same signal peptides. The BLAST 2 SEQUENECES and CLUSTAL W were used to align the two protein sequences and multi-protein sequences, respectively. The alignment result indicated that homology of these sequences with the same signal peptide was very highly conservative in amino acid of complete gene. The effect of the signal peptides in S. cerevisia on expression of foreign eukaryotic secreted proteins was discussed in the paper.