[Internal symmetry and repetitive sequences in the primary structure of IRS-proteins, endogenous substrates of insulin receptor].

A new method is developed for identification of mirror type internal symmetry in protein primary structures (named as method of internal symmetry scanning). As distinct from our earlier developed graphic method, the application of the new method allows, to identify enough fast and effective, symmetrical segments in proteins of any length, and to determine the type of internal symmetry centres (one or two amino acid residues). By this method the structure of IRS-proteins, endogenous substrates of tyrosine kinase receptors, was analysed. It has been shown that the density of internal symmetry centre distribution and the homology of antiparallel sequences in functionally important regions, which possess conservation of the primary structure (the conservative profile for IRS1-proteins was calculated in this work), are higher in comparison with the variable regions. Groups of repeating sequences in the primary structure of IRS1-proteins are found. The localization of the repeats coincides with one of symmetrical structures. These findings are in line with Chipens' hypothesis in which he established a correlation between the internal symmetry and the homologous repeats.