It was found that amino acid compositional frequencies in proteins demonstrate a pseudosymmetry pattern in respect of the genetic code arrangement as we discussed in earlier papers (Siemion and Stefanowicz, 1992a, BioSystems, 27, 77-84; Siemion and Stefanowicz, 1992b, Bull. Pol. Acad. Sci., Chem. 40, 11-20; Siemion, 1994, BioSystems, 32, 25-35). The type of pseudosymmetry observed is very similar to that found in the changes of Chou-Fasman P alpha conformational parameters within the genetic code arrangement. It is also shown that the compositional frequencies of amino acids belonging to the 'G' and 'C' families of codons (excluding UCN Ser codons) change linearly with the sequence of the one-step mutations expected by our arrangement of proper codons.