Аннотация:15 polypeptide fractions from the culture liquid of Luteococcus casei were obtained by means of solid-phase extraction on a hydrophobic sorbent with a C8 phase, followed by evaporation, lyophilization and fractionation using RP-HPLC. Only two of them (Nos. I and IV) showed reactivating activity against cells subjected to the UV-stress. Using the mass spectral analysis, the structural characteristic was obtained for fraction IV, which includes two components: Ala-Pro-Asn-Glu-Asn-Gln-Gly and Ala-Pro-Asn-Glu-Gln-Gly. In the database of primary structures of polypeptides, no similarity was found to the known full-length functional peptide molecules. In the genome of L. casei, such sequences are also not identified. Presumably, the formation of active L. casei polypeptides is associated with non-matrix synthesis, possibly with proteolysis of a large protein.