[A comparison of amino acid composition of proteins from thermophiles and mesophiles].

The thermophilic feature of thermophiles are due to the high thermostability of their proteins. In order to investigate the mechanism of the high thermostability of thermophilic proteins and compare the difference of amino acid composition between thermophilic and mesophilic proteins, 110 pairs of homologous protein sequences from thermophiles and mesophiles respectively are collected and the amino acid composition, percentage of hydrophobic amino acids, hydropathy index, percentage of charged amino acids of the two protein groups are compared. It reveals that the two groups have evidently different composition in several kinds of amino acids, and thermophilic proteins have higher average hydropathy and charged amino acids composition. A comparison of the aliphatic indices between the two protein groups indicates that the reason that thermophilic proteins have higher aliphatic index is that thermophilic proteins have higher leucine composition, and thus sheds doubt on the validity of aliphatic index. It shows that it is possible to disclose some general rules with regard to the mechanism of protein thermostability by comparing a large amount of protein sequence data.