Merozoite receptor PK66 is a surface antigen involved in parasite invasion of erythrocytes. Concentrated at the apical end prior to rupture, following which it can distribute itself entirely across the surface of the free merozoite. During invasion PK66 is excluded from the erythrocyte at, and behind, the invasion interface. PK66 expressed in mature schizonts is rapidly processed as the schizont ruptures, yielding a 42/44 kDa doublet associated with the surface merozoite. Belongs to the apicomplexan parasites AMA1 family.