FIGURE 1.

Organization and diversity of streptococcal SRRPs. (A) General architecture of the SRRP polypeptide. SP, signal peptide; SRR1/2, serine-rich repeat regions 1 or 2; BR, non-repeat binding region; LPxTG, sortase dependent cell-wall anchor signal. (B) Diversity of the SRRP glycosylation loci encoded by a subset of streptococcal species. S. pneumoniae carries only one SRRP encoding allele. S. agalactiae and S. gordonii encode two major SRRP alleles; the glycosylation island associated with each allele differs in S. agalactiae but not in S. gordonii. S. salivarius encodes two major SRRP islands that are associated with one or three SRRP alleles. Homologs of the S. salivarius gtfA and gtfB are encoded elsewhere on the chromosome. GT refers to accessory glycosyltransferases.