Mutant/mutation
The mutant lacks expression of P230.

Protein (function)
The P230 protein is a member of a small family of proteins, the 6-cysteine (cys) family of (surface) proteins. The proteins are characterized 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 organization 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 (see also 'Additional Information'). Evidence has been presented that P230 is specifically expressed in male gametocytes/gametes of P. berghei. P230 does not have a GPI anchor. In P. falciparum P230 has been shown to be located on the surface of male and female gametes and evidence has been found that P230 forms a complex with P48/45 at the surface of gametocytes and gametes.

Phenotype
Phenotype analyses demonstrate that P230 plays an important role in fertilization (male fertility factor). Motile males fail to attach to and penetrate female gametes (see phenotype description). Mutant female gametes are fertile as has been shown by cross-fertilisation with wild type male gametes. This phenotype is comparable to the phenotype of mutants lacking expression of P48/45 (see RMgm-15).

Additional information
The mutant  shows very low levels of fertilization with higher fertilization rates in the mosquito than in in vitro ookinete cultures. Mutant parasites produce low numbers of ookinetes and oocysts in Anopheles stephensi mosquitoes (see also the phenotype description 'Fertilization and ookinete'). Both the ookinetes and oocysts show a normal morphology and oocysts produce normal numbers of sporozoites that are infectious to mice.

The p230 gene forms a paralogous gene pair with the gene p230p (PB000403.00.0; PFB0400w), which are closely linked in the genome.

In P. falciparum it has been shown that male gametes with a disrupted p230 gene are incapable of interacting with erythrocytes and do not form the characteristic exflagellation centers and these mutants show a strong reduction in oocyst formation (Eksi et al, 2006, Mol. Microbiol. 61, 991-998). In the P. berghei mutants lacking P230, analyses of both exflagellating microgametocytes and free, motile male gametes in live preparations did not reveal any difference in their capacity to interact with red blood cells compared to wild type gametes and normal exflagellation centers were observed.

Table: P. falciparum gene members of the 6-cys family

Other mutants