FIG 2.

Conserved structure of S. pyogenes T antigens. The cartoon depicting the structures of four sequence-diverse T antigens shows a conserved, virtually identical tandem CnaB-type Ig-like domain configuration. The key residues involved in intramolecular isopeptide bond formation and the pilin lysine (K) are shown in stick mode. An adjacent topology diagram shows the N-terminal (blue) and C-terminal (red) domains. The isopeptide bond position in each domain is depicted as a horizontal black bar. N, N terminus; C, C terminus.