蛋白質の熱安定性と構成アミノ酸残基の役割

抄録

Proteins from thermophiles have higher thermostability than homologus proteins from mesophiles. This higher thermostability is an intrinsic property which must depend on the sequence of amino acid residues. The thermostability of thermostable proteins is due to additive hydrophobic interactions, hydrogen bonding, ionic interactions or a combination of these factors.
To elucidate the role of individual amino acid resideues in conformational stability, the stabilities of wild-type and mutant proteins differing by a single amino acid residue were compared. In the case of the tryptophan synthase α-subunit from E. coli., the conformational stability (Δ_dG)of seven proteins with different substituents at the same position in the interior of the protein was found to be correlated with the hydrophobicity of the substituent amino acid residue. The differences in Δ_dG among the wild-type and mutant proteins seemed to be caused mainly by the entropic factor, because enthalpy changes of the proteins were the same.