ИСТИНА

In the current work, bacteriolytic activity of serotransferrin was discovered. Although transferrins have been known for a long time, some of their functions are not completely clear. There is the information that transferrins can suppress the bacterial growth, however, bacteriolytic activity of these proteins has not been described before. In our experiments, human blood plasma proteins were separated to identify and study new bacteriolytic factors. It was found that the protein fraction with molecular weights between 60 and 80 kDa showed bacteriolytic activity on bacteria cells. After a few stages of chromatography the active protein was purified. Trypsinolysis of the isolated protein followed by mass spectrometry analysis allowed us to identify this protein as a serotransferrin. Purified serotransferrin demonstrates bacteriolytic activity against Escherichia coli, Micrococcus luteus, Bacillus subtilis and Bacillus megaterium cells. pH profiles of activity are characterized at a maximum pH of 8.7–8.9. At an optimal pH value (8.8), the rates of lysis of various bacteria in the presence of serotransferrin and lysozyme were compared, considering the rate of lysis as a percentage of “lysozyme activity against E. coli”. Lysozyme at a concentration of 0.3 lg/mL acts effectively against E. coli (100%) and M. luteus (68%), less efficiently against B. subtilis (18%) and practically does not act at all against B. megaterium (1%). Serotransferrin at a concentration of 3 lg/mL acts effectively against E. coli (61%), less efficiently against M. luteus and B. subtilis (13% and 12%), but relatively efficiently against B. megaterium (23%). The detailed investigation of serotransferrin bacteriolytic properties can be useful in drug-design to fight antibiotic-resistant pathogenic microorganisms. The authors thank Dr Marina Serebryakova, leading researcher of the Belozersky Institute of Physico-Chemical Biology, for conducting a mass spectrometric study.