FIG. 5.

The A, B, C, and D repeat regions of M protein, with the protein anchor and pepsin cleavage site shown. The A repeat region varies between serotypes and contains the highly variable serotype-specific amino acid sequence of M protein at the N terminus. The B repeat region varies from serotype to serotype, while the C repeat region contains a conserved sequence shared among all of the serotypes. The anchor region contains the LPXTGX motif required to anchor gram-positive proteins in the cell membrane. (Reprinted from reference 119 with permission from the publisher.)