Amino acid complementarity: testing of hypotheses.

To determine whether hypotheses about the complementarity of amino acids based on the genetic code reflect the amino acid contact preferences found in natural proteins, the average contact probabilities for hypothetical complementary amino acid pairs were compared with those for all possible remaining pairs of the corresponding subset. A statistically significant preference was found for contact between amino acids with codons which had the same central nucleotide. Conversely, the contact probabilities for amino acids with complementary codons either did not exceed, or exceeded only insignificantly, the value for the corresponding remainder subset. The data obtained do not support the hypothesis for the complementarity of peptides coded by complementary RNA strands.