Crystal structure of an NPNA-repeat motif from the circumsporozoite protein of the malaria parasite Plasmodium falciparum.

A crystal structure is reported of the peptide Ac-Ala-Asn-Pro-Asn-Ala-NH2, representing the immunodominant region of the major surface protein on the malaria parasite; the NPNA motif adopts a type-I beta-turn, which is stabilized by hydrogen bonding between the CO of Asn2 and the NH of Ala5 as well as between the O(delta) of Asn2 and the NH of Asn4.