Chou-Fasman conformational amino acid parameters and the genetic code.

It was found that the distribution of Chou-Fasman P alpha conformational parameters within the genetic code (arranged into the one-step mutation ring) may be described by a quite simple trigonometric function of mutational angle. The mutational angle is defined as k pi/32, where k is a number of codons count from i under consideration to k. The principal eight-codon periodicity defines the P alpha-genetic code correspondence, but the other perioditicies seem also to modulate the principal function. The eight-codon periodicity finds the explanation in the regular changes of third bases of successive codons. These changes appear in the order; C,U,A,G,G,A,U,C, assigning eight maxima and eight minima of P alpha curve. The experimental P alpha values fit well the dependence found, except proline, the amino acid which breaks the regular eight-codon P alpha periodicity. The analysis of dependence obtained suggest that, in agreement with the hypothesis of Jukes (1973), arginine CGR and AGR codons could be in an earlier genetic code used for coding of ornithine.