Mutant/mutation
The mutant lacks expression of the ookinete surface protein P28.

Protein (function)
P28 is one of two major surface proteins (P25 and P28) of the plasma membrane of ookinetes. The proteins are conserved between different Plasmodium species. The proteins are characterized by a secretory N-terminal signal sequence followed by three or four epidermal growth factor (EGF) domains and a glycosylphosphatidylinositol (GPI) anchor. Synthesis of both proteins begins between 0.5 and 2 h after the formation of the female gametes, and the proteins are still present in young oocysts. The paralogous genes encoding P25 and P28 are located next to each other in the genome in a head to tail organization.

Phenotype
The phenotype analyzes show only a minor effect on ookinete and oocyst development, indicating a redundancy in function of P25 and P28 (see also mutant RMgm-3 that lacks expression of both P25 and P28).

Additional information
Motility and entry into insect cells in vitro of ookinetes lacking expression of P28 are normal, but the number of ookinetes successfully transforming into oocysts in vitro was significantly reduced (Siden-Kiamos et al., J. Cell Science (2000) 113, 3419-26).

Other mutants
A. P. berghei mutant has been generated lacking P25 (RMgm-2).
A. P. berghei mutant has been generated lacking both P28 and P25 (RMgm-3).