FIG 6.

Substrate binding of NA proteins via the 2nd SIA-binding site. (A). HN and HB NA proteins and N9 proteins with different binding properties (10) were complexed to lumazine synthase nanoparticles displaying domain B of protein A using anti-Strep-tag monoclonal antibodies. Limiting dilutions of these complexes were incubated with red blood cells in the presence of OsC, and hemagglutination titers were determined. Standard deviations are indicated. (B and C) Membrane vesicles containing full-length HN, HN N369H, or HB protein were analyzed for their ability to bind 3′-SLNLNLN or 6′-SLNLNLN in the presence of OsC using biolayer interferometry. Representative experiments are shown.