嗜热与嗜常温微生物的蛋白质氨基酸组成比较

嗜热微生物的嗜热特性与其蛋白质的高度热稳定性紧密相关。为了探索嗜热蛋白质的热稳定机制，比较嗜热和嗜常温微生物的蛋白质在氨基酸组成上的差别，收集110对分别来自嗜热和嗜常温微生物的同源蛋白质序列，比较两组蛋白质各种氨基酸含量以及疏水性氨基酸组成、疏水性指数和荷电氨基酸组成的差别，结果两者在多种氨基酸含量上存在微小但统计学上显著的差别，嗜热蛋白质比嗜常温蛋白质具有较高的平均疏水性和荷电氨基酸组成。对两组蛋白质的“脂肪族氨基酸指数”进行分析，证明嗜热蛋白质之所以具有较高的脂肪族氨基酸指数是由于其亮氨酸含量较高，与影响该指数的其它几种氨基酸无关；从而认为该指数的意义值得怀疑。通过对大量同源嗜热蛋白质和嗜常温蛋白质氨基酸组成的比较，能够揭示一些有关蛋白质热稳定性的普遍规律。

A COMPARISON OF AMINO ACID COMPOSITION OF PROTEINS FROM THERMOPHlLES AND MESOPHILES

The thermophilic feature of thermophiles are due to the high thermostabilityof their proteins. In order to inveshgate the mechanism of the high thermostability ofthermophilic proteins and compare the difference of amino acid composition betweenthermophilic and mesophilic proteins, 110 pairs of homologous protein sequences fromthermophiles and mesophiles respechvely are collected and the amino acid composition,percentage of hydrophobic amino acids, hydropathy index, percentage of chargedamino acids of the two protein groups are compared. It reveals that the two groupshave evidently different composihon in several kinds of amino acids, and thermophilicproteins have higher average hydropathy and charged amino acids composition. Acomparison of the aliphahc indices between the two protein groups indicates that thereason that thermophilic proteins have higher aliphahc index is that thermophilicproteins have higher leucine composition, and thus sheds doubt on the validity ofaliphatic index. It shows that it is possible to disclose some general rules with regardto the mechanism of protein thermostability by comparing a large amount of proteinsequence data.