The rapid evolution of signal peptides is mainly caused by relaxed selection on non-synonymous and synonymous sites
The rapid evolution of signal peptides is mainly caused by relaxed selection on non-synonymous and synonymous sites
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信号肽的快速进化主要是由于非同义和同义位点的宽松选择造成的
DOI：
10.1016/j.gene.2009.01.015
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发表时间：
2009-05-01
期刊：
影响因子：
3.5
通讯作者：
Li, Yong-Quan
中科院分区：
文献类型：
--
作者：
Li, Yu-Dong;Xie, Zhong-Yu;Li, Yong-Quan
分泌蛋白的前体通常含有一个n端信号肽（SP），它指导蛋白质穿过膜。我们对原核生物和真核生物的分泌蛋白进行了全基因组分析，发现信号肽的进化速度比成熟蛋白快。为了确定进化模式是否可以用选择压力的变化来解释，我们研究了信号肽中的氨基酸替换。我们发现它们往往比那些在蛋白质的成熟区域更保守，表明放松的选择压力作用于非同义位点。这可能是由信号肽相似的生化需求来解释的。我们还观察到密码子适应指数（CAI）下降，表明信号肽同义位点的纯化选择放松。此外，信号序列的进化速率随着密码子使用偏倚的增加而增加，这表明信号肽中稀有密码子频率的增加是自然选择的结果，以提高分泌效率。也有证据表明信号肽可能经历了正向选择。综上所述，信号肽的进化可能是由多种选择力混合引起的，主要是纯化选择的放松。(C) 2009 Elsevier B.V.版权所有
The precursor of a secretory protein usually contains an N-terminal signal peptide (SP), which directs the protein to cross the membrane. We performed a genome-wide analysis of secretory proteins in prokaryotes and eukaryotes, and found that signal peptides evolved faster than mature proteins. To determine whether the evolutionary pattern could be explained by selective pressure changes, we studied the amino acid replacements in signal peptides. We found that they tend to be more conserved than those in mature regions of the proteins, suggesting relaxed selective pressure acting on non-synonymous sites. This is potentially explained by similar biochemical requirements of signal peptides. We also observed a decreased codon adaptation index (CAI), suggesting a relaxed purifying selection on synonymous sites of signal peptides. In addition, the evolutionary rate of signal sequences increases with codon usage bias, suggesting that increased rare codon frequency in signal peptides is a result of natural selection to improve secretion efficiency. Evidence also suggests signal peptides might have undergone positive selection. In summary, the evolution of signal peptides may be caused by a mixture of selection forces, primarily relaxation of purifying selection. (C) 2009 Elsevier B.V. All rights reserved.