RESUMO
Lysin 2638aR and chimeric Ply187AN-KSH3b fusion protein are capable of lysing antibiotic-resistant strains of Staphylococcus aureus and are promising alternatives to antibiotics. Studies on the stability and structure of lysins 2638aR and Ply187AN-KSH3b are important for assessing the feasibility of their practical use. Both lysins are highly active at physiological pH (7.5) and at low salt content (the concentration of NaCl in the reaction medium is not more than 250â¯mM). Lysins are inactivated by a monomolecular mechanism and have high stability at 4⯰C (storage temperature). The maximum value of the half-inactivation time for lysin 2638aR is 190-200 days (500-1000â¯mM NaCl, pH 6.0-7.5), for lysin Ply187AN-KSH3b is 320-340 days (10-1000â¯mM NaCl, pH 6.0). The lysins are pretty stable in human blood serum (the half-inactivation time is 0.5-2â¯h) at 37⯰C. The lysins undergo denaturation in large part due to the destruction of the α-helices at temperatures above 40⯰C.