Interaction between two domains of the P-yoelii MSP-1 protein detected using the yeast two-hybrid system

Several model systems of plasmodia have demonstrated the potential of the m erozoite surface protein, MSP-1, to induce protective immunity. However, li ttle is known about the function of this protein or its interaction with ot her surface molecules that may also serve as immunological targets. To iden tify potentially significant inter- and intra-molecular interactions involv ing MSP-1, we have utilized the yeast two-hybrid system. A cDNA activation domain library was constructed from the erythrocytic stages of the murine m alarial parasite Plasmodium yoelii yoelii 17XL. A 795 by region of Py17XL M SP-1 (bait), homologous to the Plasmodium falciparum MSPI33 fragment, was i nserted into a Gal4p DNA binding domain vector and used to screen the activ ation domain library (target). Several randomly selected clones that demons trated bait-target interaction were found to express overlapping regions of Py17XL MSP-1. Deletion constructs further localized the peptide fragments retaining interaction indicating that a region within the MSP-I-38 fragment interacts with the MSP-1 bait domain. Subsequent studies confirmed this in teraction, as both peptides were co-precipitated from cell lysate by a pept ide tag-specific antibody. It was observed that the interaction of these tw o fragments significantly increased the half-life of the MSP-1(38) within y east cells. The specific interaction described here demonstrates the potent ial of this approach to elucidate additional inter- or intra-molecular inte ractions of Py17XL MSPI and other malarial proteins. (C) 2001 Elsevier Scie nce B.V. All rights reserved.