FIGURE 7.

Mutations in CCP 1 of CR1 abrogate PfRh4 binding. A, supernatants containing His-tagged CR1 recombinant constructs were injected at 220 nm over immobilized PfRh4 (3,300 RU). Reference subtracted sensorgrams demonstrate that LHR A Δ1, m18, and m20 behave like LHR B and do not bind to immobilized PfRh4. A parallel flow cell bearing 4,000 RU immobilized mouse IgG was employed as the reference. B, duplicate injections of supernatants containing His-tagged constructs passed over immobilized PfRh4 demonstrate that m7–9,18–20r carrying six single amino acid substitutions from LHR A confers a PfRh4-binding site if placed in homologous positions of LHR B. Consistent with ELISA and IP results, m7–9,18–20 protein has a many-fold greater affinity for PfRh4 than LHR A.