FIG. 2.

Fusion proteins derived from the CS2 var gene sequence were assayed for direct interaction with CSA. (A) The CIDRb and DBL3 fusion proteins interacted with CSA, whereas the CIDRa protein showed no activity. ⧫, CIDRa; ■, CIDRb; ●, DBL3. (B) The end regions of DBL3 had independent CSA binding activity, but the center region did not bind. ⧫, DBL3-5′; ▴, DBL3-C; ■, DBL3-3′. (C) Reduction and alkylation of CIDRb and DBL3 proteins substantially reduces their affinity for CSA. ⧫, CIDRb; ■, CIDRb reduced and alkylated; ▴, DBL3; ●, DBL3 reduced and alkylated. All results are mean and standard error of the mean for three independent assays.