FIG. 5.

Cofactor activity of FH bound to bacteria expressing wild-type or mutated YadA. Bacteria were preincubated with FH (30-μg/ml final concentration) (left) and washed. Subsequently, the bacteria were exposed to factor I and C3b. The bacterial surface-bound FH is indicated by the asterisk, while in the control panel (right), reactions were carried out without bacteria. C3b and its cleavage products from the supernatants were detected using a mixture of rabbit anti-C3c and anti-C3d antisera. Inactivation of C3b can be seen by the reduced intensity of the C3b α′-chain and the appearance of α′-chain cleavage fragments of 67, 43, and 41 kDa. FH bound to the bacteria was detected from pellets by immunoblotting using preadsorbed goat anti-FH antiserum.