<div><p>Fusion proteins, derived from the HVR of M4.1 or M114 and the C-terminal part of M5, were expressed in the M-negative strain S. pyogenes ΔM5 using genes carried on plasmid pLZ12Spec. Controls included a strain expressing the C4BP-binding fusion protein M22<sup>57</sup>–M5, a strain expressing the non–C4BP-binding M5 protein, and the M-negative strain ΔM5.</p><p>(A) Surface expression analyzed with rabbit antibodies directed against the C-repeat region of M5. Bound antibodies were detected with radiolabelled protein A. Binding of protein A to the M22<sup>57</sup>–M5 strain, incubated with antiserum diluted ×10<sup>2</sup>, was defined as 100%. The M5-negative strain ΔM5 served as negative control.</p><p>(B) Binding of radiolabelled C4BP. Binding at the highest bacterial concentration to the control expressing M22<sup>57</sup>–M5 was defined as 100%. The non–C4BP-binding M5 strain served as negative control. All data in (A) and (B) are based on three separate experiments with duplicate samples, and are presented as means ± SD.</p></div
