SUB1-ProM is expressed in the PV or at the merozoite surface in P. falciparum schizonts. IFA of mature P. falciparum 3D7 schizonts probed with the indicated antibodies. The merged images are presented both with and without the nuclear stain DAPI. The anti-SERA5 pattern is typical of a PV location, whilst the merozoite surface protein MSP4 delineates the plasma membrane of intracellular segmented merozoites. Note that the distance between the merozoite plasma membrane and PV membrane is generally too small to be resolved by light microscopy. Both signals show extensive co-localisation with the SUB1-ProM signal, which is more evident with the anti-MSP4 signal. Scale bar, 5 mm. IFA produced a signal typical of a PV or merozoite surface location, overlapping with the established PV marker SERA5 (which is also a major endogenous substrate of PfSUB1.

Tarr SJ, Withers-Martinez C, Flynn HR, Snijders AP, Masino L, Koussis K, Conway DJ, Blackman MJ. A malaria parasite subtilisin propeptide-like protein is a potent inhibitor of the egress protease SUB1. Biochem J. 2020 Jan 16. pii: BCJ20190918.