RESUMO
It is established that the sequences of all different proteins from E. coli ribosome as well as two protein biosynthesis initiation factors, two ribosome-associated DNA-binding proteins, and the elongation factor EF-Tu from the same source possess a periodicity expressed more weakly and different from that found earlier for a number of proteins representatives of 18 superfamilies. The statistical significance of the periodicity observed was checked by comparing the area below the periodicity curve of every protein examined with that of computer generated sequences having the same amino acid composition and length. The results concerning the proteins from small and large ribosomal subunit are compared. The conclusions support and supplement the concept about the presence of a trend in protein molecular evolution from universal (Gly, Ala) to specialized (Phe, Tyr, Trp, Cys) amino acids.