Fig. 4.

Immunolocalization of plasminogen on the ookinete surface and competition with the lysine-motif peptide (100%). (A) (Upper) Nonpermeabilized cultured P. berghei ookinetes were incubated with a mixture of antiplasminogen (Plg; green) and anti-Pbs21 (red) antibodies. Nuclear staining with DAPI is shown in blue. DIC, differential interference contrast microscopy. (Lower) Similar experiment with cultured P. falciparum ookinetes, except that anti-Pfs28 (red) antibodies were used instead of anti-Pbs21. One hundred percent of the ookinetes that stained with the anti-Ps21 or anti-Pfs28 antibodies also stained with plasminogen. (B) (Upper) Plasminogen binding to the P. berghei ookinete surface is competed by the lysine-motif peptide DKSLVK. Peptide concentrations were as indicated in each panel. (Lower) DIC images of the ookinetes shown.