Binding of recombinant F2 and chymotryptic F2 fragments to glycophorin A in pull-down assays. Recombinant F2 was used in pull-down assays with glycophorin A before and after treatment with chymotrypsin. Recombinant F2 and chymotrypsin-treated F2 were incubated with glycophorin A to allow binding. F2 fragments bound to glycophorin A were precipitated using a mouse monoclonal antibody raised against glycophorin A and protein A-Sepharose. Bound F2 fragments were separated by SDS-PAGE and detected by Western blotting using rabbit sera raised against recombinant F2. MW indicates prestained molecular weight markers shown in kDa; lane 1, full-length recombinant F2 used for pull-down assays; lane 2, pull-down assay with recombinant F2 and glycophorin A; lane 3, pull-down assay with chymotrypsin-treated F2 (incomplete proteolysis) and glycophorin A; lane 4, chymotrypsin-treated F2 (incomplete proteolysis) used for pull-down assay; lane 5, control pull-down assay using recombinant F2 and BSA instead of glycophorin A; lane 6, full-length recombinant F2; lane 7, chymotrypsin-treated F2 (complete proteolysis); lane 8, pull-down assay with chymotrypsin-treated F2 (complete proteolysis) and glycophorin A.