Comparative analysis of specificity in protein-protein interactions. Part II.: The complementary coding of some proteins as the possible source of specificity in protein-protein interactions.

Anterior pituitary peptides and some other human hormones were analyzed by a computerized step-by-step comparative method for the frequency and distribution of some specific amino acids with the property of having been coded by complementary nucleic acid triplets in the DNA. There are 26 such amino acid pairs, which are only 13% of the available 200 pairs. Several protein parts have been found, both in intra- and intermolecular comparisons, to contain such amino acid pairs with a significantly higher frequency than could be explained only on the basis of a random distribution. During the self-comparisons of the hormones, ring-like states have been found in which 22-66% of the available amino acid pairs were complementarily coded. It was suggested that the molecular background of Informational Complementarity (IC) of amino acids and proteins (see part I.) may be their complementary coding.