Binding of CFH, CFHR-1, and PLG to BpcA. (A) Microtiter plates were coated with BpcA, BtcA, or BhCRASP-1 and incubated with either CFH, normal human serum (as a source of CFHR-1), or PLG. Binding was detected using goat anti-CFH, the CFHR-1-specific MAb JHD8, or goat anti-PLG immune serum, followed by the respective horseradish peroxidase (HRP)-conjugated IgGs. (B) Microtiter plates were coated with purified recombinant BpcA protein and various deletion mutants thereof and were then incubated with CFH, normal human serum (as a source of CFHR-1), or PLG. Binding was detected using goat anti-CFH, the CFHR-1-specific MAb JHD8, or goat anti-PLG immune serum, followed by the respective HRP-conjugated IgGs. (C) Diagrammatic representation of native and expressed recombinant BpcA proteins and their binding characteristics for the serum proteins CFH, CFH-1, and PLG as determined by ligand affinity blot analysis and ELISA. Numbers refer to amino acid residues.