S. equi Mac Gene
S. equi genome encodes a Mac homologue SeMac. The protein shares 62.4% identity in amino acid sequence with Mac made by serotype M1 GAS and a putative secretion signal sequence (amino acids 1-34), and the catalytic residues of GAS Mac consisting of Cys94, His262 and Asp284 are conserved in SeMac (Cys102, His272 and Asp 294) (Fig. 1). To test whether other S. equi strains have the mac gene, 10 S. equi isolates representing various geographic locations were tested with PCR using mac-specific primers. All the strains tested had the mac gene (Fig. 2). DNA sequencing found that the mac gene is 100% conserved in DNA sequence in these strains.