This invention discloses a lysin that can kill many species of Streptococci. A new lysin, ClyR, was constructed by the gene splicing method. The ClyR can effectively kill different species of Streptococci, including Streptococcus pneumoniae, Streptococcus pyogenes, Streptococcus suis, Streptococcus uberis, Streptococcus agalactiae, Streptococcus dysgalactiae, Streptococcus mutans, Streptococcus equi, and various Enterococci and Staphylococcus aureus. ClyR shows good stability and is not sensitive to EDTA and high concentration of NaCl. Moreover, the ClyR is active in a wide range of pH and maintains high activity in pH 5-11. Recombinant protein ClyR is well expressed in E. coli stain BL21 (DE3). High doses of ClyR showed no apparent toxicity in mice. Furthermore, administration of 0.8 mg per mouse once is able to completely protect the mouse infected with lethal doses of Group B Streptococci. The ClyR can be used alone or in combination with different forms of reagents and solutions, for the control of a variety of Streptococci and for the treatment of infections caused by these bacteria. It has a broad application prospect.
