A time course of merozoite invasion of the erythrocyte from egress through postinvasion. (A) A cellular overview is given with associated timing of organelle secretion and key mechanistic or signaling steps listed below. After apical reorientation, the merozoite establishes a tight junction that is marked by RON4 and AMA1. The tight junction is ultimately connected to the actomyosin motor, although the exact nature of this has yet to be established. As the tight junction moves across the merozoite surface, proteins are shed into the supernatant through the activity of proteases such as ROM4, ROM1, SUB1, and SUB2. The parasitophorous vacuole and membrane are formed primarily from the rhoptries, although some red cell membrane components are included, which expel their contents, forming the space into which the parasite can move under the action of the actomyosin motor. Once the tight junction reaches the posterior end of the parasite, the membranes seal by an as yet unknown mechanism.