Mutant/mutation
The mutant expresses a C-terminal mCherry-tagged version of P36.

Protein (function)
P52 (P36p) and P36 are members of a small family of proteins, the 6-cysteine (cys) family of (surface) proteins (Thompson J. et al., Mol. Biochem. Parasitol. (2001)118, 147-54). The proteins are characterised by domains of roughly 120 amino acids in size that contain six positionally conserved cysteines (6-cys). Although some species of Plasmodium (may) contain unique members of the 6-cys family, ten members have been identified that are conserved both in structure as well as in genome organisation throughout the genus. Some of the conserved 6-cys proteins are encoded by genes that form paralogous gene-pairs which are closely linked in the genome separated by less then 2 kb of intergenic region. Most members have a GPI anchor and are predicted membrane surface proteins whereas others appear to be secreted and most members are expressed in a discrete stage-specific manner in gametocytes, sporozoites or merozoites.
Both genes have been shown to play a role in invasion/development of sporozoites in hepatocytes (see PF3D7_0404400 and PF3D7_0404500.

Phenotype
P36mCherry parasites successfully progressed through development within the mosquito vector, with an in vivo pre-patent period comparable to wild-type parasites; in vitro, sporozoites displayed normal gliding motility ( and were capable of invading hepatoma cells, indicating no significant negative impact on protein function derived from the fusion with the mCherry tag.

P36mCherry was found to be expressed in both oocyst (day 10) and salivary gland-derived sporozoites by live fluorescence microscopy and confirmed by western blot analysis using α-mCherry.

P36mCherry is expressed at significantly higher levels in salivary gland sporozoites as compared to oocyst sporozoites. P52, however, was only detected in salivary gland sporozoites. Evidence is presented for a micronemal location of P36mCherry and for the co-localization of P36 with P52 and/or TRAP in the micronemal organelles.

Analysis of P36mCherry salivary gland sporozoites by IFA in the context of Hepa 1–6 cell invasion revealed the presence of an accumulation of P36mCherry protein toward one end of the sporozoite, reminiscent of the previously reported secretion of TRAP.
This concentrated protein appeared to be released from the sporozoite when contrasted with the MTIP-labeled inner membrane complex, and it consistently co-localized with unprocessed, full-length TRAP. The staining pattern for both P36mCherry and TRAP regularly overlapped at what appeared to be progressive stages of secretion where the concentration of the proteins at the apical end became more prominent as the internal micronemal signal diminished. 

From the paper:  
'Here we show that parasites with a single P52 or P36 gene deletion each lack a PV after hepatocyte invasion, thereby pheno-copying the lack of a PV observed for the P52/P36 dual gene deletion parasite line. This indicates that both proteins are equally important in the establishment of a PV and act in the same pathway. We created a Plasmodium yoelii P36mCherry tagged parasite line that allowed us to visualize the subcellular localization of P36 and found that it partially co-localizes with P52 in the sporozoite secretory microneme organelles. Furthermore, through co-immunoprecipitation studies in vivo, we determined that P36 and P52 form a protein complex in sporozoites, indicating a concerted function for both proteins within the PV formation pathway. However, upon sporozoite stimulation, only P36 was released as a secreted protein while P52 was not. Our results support a model in which the putatively glycosylphosphatidylinositol (GPI)-anchored P52 may serve as a scaffold to facilitate the interaction of secreted P36 with the host cell during sporozoite invasion of hepatocytes.'

Additional information
For P36 and P52 labeling, about a third (33%) of the counted micronemes in sporozoites were dually labeled, and a similar number were labeled only with P36 (34%); however, only 15% of the total number of micronemes was singly labeled with P52. In other words,
approximately half of the micronemes (F = 0.49) labeled with P36 were also labeled with P52, while more than two thirds (F = 0.68) of all P52-labeled micronemes were simultaneously labeled with P36. For P36 and TRAP, out of all micronemes labeled with TRAP, 42% also contained P36; and about 58% of all P36-labeled micronemes were also labeled with TRAP. For P52 and TRAP, there was a similar percentage of single and double labeled micronemes containing TRAP; however, the majority of all P52-labeled micronemes (nearly 88%) were also labeled with TRAP. Rather than reflecting a random distribution, these findings are indicative of an intrinsic higher probability for P52 to be localized in micronemes containing either TRAP or P36, instead of being found individually. Evidence is presented that P36 Interacts With P52 but not With TRAP.

Other mutants
see PF3D7_0404400 and PF3D7_0404500