Toward the elucidation of the mechanism of attachment and entry of malaria sporozoites into cells: synthetic polypeptides from the circumsporozoite protein of Plasmodium falciparum bind Ca2+ and interact with model phospholipid membranes.

Through the joint use of CD, Fourier transform ir (FTIR), and attenuated total reflectance FTIR we have found that synthetic polypeptide models of the Plasmodium falciparum circumsporozoite (CS) protein repeat domain bind calcium ions in helicogenic environments. Ca(2+)-(NANP)n complexes (n greater than or equal to 20) interact vectorially with model phospholipid membranes orienting their polypeptide axes preferentially along those of the lipid acyl chains. It is proposed that the P. falciparum CS protein central region, rather than acting as a molecular lure helping the parasite to evade host immune control, plays, as a specific Ca2+ macroligand, a critical functional role during attachment, invasion, and development of the malaria parasite in the hepatic cell.