Structure-dependent relationships between growth temperature of prokaryotes and the amino acid frequency in their proteins.

We studied the amino acid frequency and substitution patterns between homologues of prokaryotic species adapted to temperatures in the range 0-102 degrees C, and found a significant temperature-dependent difference in frequency for many of the amino acids. This was particularly clear when we analysed the surface and core residues separately. The difference between the surface and the core is getting more pronounced in proteins adapted to warmer environments, with a more hydrophobic core, and more charged and long-chained amino acids on the surface of the proteins. We also see that mesophiles have a more similar amino acid composition to psychrophiles than to thermophiles, and that archea appears to have a slightly different pattern of substitutions than bacteria.