Latent periodicity of 21 bases typical for MCP II gene is widely present in various bacterial genes.

The existence of a typical latent periodicity of 21 bases from the Tar chemoreceptor gene of Escherichia coli (E. coli) (MCP II) in the bacterial genes has been investigated in this work. Among 583 annotated bacterial genes and ORFs in the GenBank, in which the typical periodicity has been found, the chemoreceptors' genes constituted the most numerous group (18.5%). This typical latent periodicity of 21 bases has been revealed in many different genes of regulatory proteins, DNA polymerases, reductases, kinases and others. The numbers in such gene groups varied from 1 to 4% of the total analyzed genes. The 2D-structures analysis of the amino acid residues, which have been translated from the genes' regions with 21 bases periodicity, has shown that, though the enrichment of alpha-helical structures in such sequences is kept in all cases, it is seen that the latent periodicity of 21 bases is a very sensitively tuned basis, allowing the translated residues to smoothly change from one conformation to another. Interesting results have been obtained for 16S rRNAs genes of proteobacteria. Short sequences-determinants have been revealed in the genes, which select beta and gamma proteobacteria with an accuracy of above 90%.