Protein andDNAThermostability

Abstract

Adaptation to different environmental temperatures establishes specific requirements on the stability of DNA and protein macromolecules. Organismal strategies of thermophilic adaptation, structure‐ and sequence‐based, and their physical origins provide a consistent picture of the evolution of protein thermostability. A strong correlation between the optimal growth temperature (OGT) and the frequency of ApG dinucleotides in both sense and antisense strands of genomic DNA along with the absence of any “thermophilic” bias in the nucleotide composition highlights a key role of base stacking in the thermostabilization of the DNA double helix. The codon bias provides an excess of ApG pairs, which ensures the thermophilic adaptation of genomic DNA. The concentration of seven amino acids, Ile, Val, Tyr, Trp, Arg, Glu, Leu (IVYWREL), serves as a universal proteomic predictor of the OGT prokaryotes. The IVYWREL combination manifests a generic “thermophilic” trend in amino acid composition: the increase of hydrophobic and charged residues at the expense of polar ones. This so‐called “from both ends of the hydrophobicity scale” trend is a result of the positive (stabilizing the native state) and the negative (destabilizing misfolded conformations) components of protein design. The pressure to preserve energies of important native and non‐native contacts results in a correlation in mutations of amino acid residues involved into these contacts. A comparison of energy (Myiazawa–Jernigan potential) and substitution (BLOSUM62) matrices reveals a high rate of substitutions between amino acids that strongly attract each other (native contacts) and between residues that strongly repel each other (non‐native contacts).