Identification of MMP-like protein from Streptococcus mitis

Streptococcus mitis is a normal commensal of the human oral cavity and oropharynx. This microorganism is an opportunistic pathogen in immune compromised hosts and a cause of invasive diseases such as infective endocarditis. We isolated a matrix metalloprotease (MMP)-like protein of S. mitis. The gene for the MMP-like protein was found on the genome sequence database of S. mitis . The gene encodes a protein consisting of 240 amino acid residues with a conserved zinc-binding motif (HEXXHXXGXXH) among the matrix metallopeptidase family. The gene was PCR-amplified from S. mitis ATCC 49456 and cloned for construction of the recombinant protein. The recombinant MMP-like protein with a GST-tag was purified and the enzymatic activity was assessed. The recombinant protein showed approximately half the level of MMP-like activity as compared to human recombinant MMP-8. The MMP-like protein of S. mitis may be involved in the pathogenesis of infection to the dentin with collagen fibers and systemic invasive diseases.