Structural features of collagens of warm-blooded and cold-blooded animals that determine differences in their thermal stability.

We have previously shown that the thermal stability of animal collagens correlates with the number of hydrophobic amino acid residues in their composition: the more hydrophobic residues in a molecule, the higher the denaturation temperature of collagen. In addition, it was found that with the same hydrophobicity, the thermal stability of collagens of cold-blooded animals can be several degrees lower than that of warm-blooded animals. To understand the reasons for this, we studied the amino acid composition and sequences of α1, α2, and α3 chains of type I collagen in warm-blooded and cold-blooded animals. The α3 chain is found only in cold-blooded animals and is represented by sequences for only 6 fish species. The results of the study show that differences in the thermal stability of collagens of warm-blooded and cold-blooded animals may be due to differences in the number of Gly-Gly pairs, Pro, Ala, Met, Ser in collagen subunits. A negative correlation was observed between the number of GGY (Gly-Gly-Yaa, pair Gly-Gly is before Yaa in the sequence) and GGX (pair Gly-Gly is before Xaa in the sequence) and collagen thermal stability. Differences in the amounts of GGY and GGX were also observed between the different types of α1, α2, and α 3 chains. A negative correlation with thermal stability was also observed for Ser. For all chain types, the amount of Pro at position Xaa and Pro at position Yaa was shown to correlate with collagen denaturation temperatures. Moreover, in the α1 and α2 chains of warm-blooded and cold-blooded animals, the positive correlation with Pro(Yaa) was higher than with Pro (Xaa). Similarities were found between the α1 and α3 chains and their differences from the α2 chain in the amount and ratio of Pro (Xaa) and Pro (Yaa).