Structure of thePlasmodium6-cysteine s48/45 domain

Abstract

The s48/45 domain was first noted in Plasmodium proteins more than 15 y ago. Previously believed to be unique to Plasmodium , the s48/45 domain is present in other aconoidasidans. In Plasmodium , members of the s48/45 family of proteins are localized on the surface of the parasite in different stages, mostly by glycosylphosphatydylinositol-anchoring. Members such as P52 and P36 seem to play a role in invasion of hepatocytes, and Pfs230 and Pfs48/45 are involved in fertilization in the sexual stages and have been consistently studied as targets of transmission-blocking vaccines for years. In this report, we present the molecular structure for the s48/45 domain corresponding to the C-terminal domain of the blood-stage protein Pf12 from Plasmodium falciparum , obtained by NMR. Our results indicate that this domain is a β-sandwich formed by two sheets with a mixture of parallel and antiparallel strands. Of the six conserved cysteines, two pairs link the β-sheets by two disulfide bonds, and the third pair forms a bond outside the core. The structure of the s48/45 domain conforms well to the previously defined surface antigen 1 (SAG1)-related-sequence (SRS) fold observed in the SAG family of surface antigens found in Toxoplasma gondii . Despite extreme sequence divergence, remarkable spatial conservation of one of the disulfide bonds is observed, supporting the hypothesis that the domains have evolved from a common ancestor. Furthermore, a homologous domain is present in ephrins, raising the possibility that the precursor of the s48/45 and SRS domains emerged from an ancient transfer to Apicomplexa from metazoan hosts.

Translational repression of the cpw-wpc gene family in the malaria parasite Plasmodium

“…Each domain typically contains 6 cysteines, likely paired in disulfide bridges, which is reminiscent of other cysteine-rich apicomplexan domains such as the COWP protein family of the oocyst wall in coccidians [26,27]; the 6-Cys family that includes the Plasmodium gamete proteins Pfs230, Pfs47 and Pfs48/45 [28][29][30][31]; and the Toxoplasma SAG proteins [28,30,31]. The cpw-wpc gene family is widely conserved among apicomplexans, including Table 3).…”

Structural and Biochemical Characterization of Plasmodium falciparum 12 (Pf12) Reveals a Unique Interdomain Organization and the Potential for an Antiparallel Arrangement with Pf41

“…Since their identification, 6-Cys domains have been found in proteins expressed on all Plasmodium lifecycle stages (4). More recently, homologues have been identified in all members of the aconoidasidan clade in the phylum Apicomplexa (5). The 6-Cys s48/45 domain is presented in copy numbers of 1-14 and generally in tandem pairs of A-type and B-type domains, termed Plasmodium gamete surface homology fragments (4).…”

“…The 6-Cys s48/45 domain is presented in copy numbers of 1-14 and generally in tandem pairs of A-type and B-type domains, termed Plasmodium gamete surface homology fragments (4). Of the 12 s48/45 domain-containing proteins in P. falciparum (5), only a select few have a known function. Two are essential to male/female gamete fusion (Pfs48/45 and Pfs230) (6 -8), and one of these is also important for male gamete exflagellation and interaction with erythrocytes (Pfs230) (9), whereas others (Pf36 and Pf52) have roles in sporozoite infection of hepatocytes and replication therein (10,11).…”

Steps toward a globally available malaria vaccine

“…Pfs48/45 contains a glycosylphosphatidylinositol (GPI) anchor that attaches the protein to the surface of the gamete creating a platform for the soluble Pfs230 protein to attach and allow for zygote formation. 4,5 The 6-cysteine domain structure present in both Pfs48/45 and Pfs230 is also found within surface proteins associated with the other life stages of the P. falciparum lifecycle including the preerythrocytic sporozoites and the erythrocytic merozoites. 4 Since exposure to Pfs48/45 induces natural immunity and antibodies elicited by both Pfs48/45 and Pfs230 have research has focused largely on this species.…”

“…4,5 The 6-cysteine domain structure present in both Pfs48/45 and Pfs230 is also found within surface proteins associated with the other life stages of the P. falciparum lifecycle including the preerythrocytic sporozoites and the erythrocytic merozoites. 4 Since exposure to Pfs48/45 induces natural immunity and antibodies elicited by both Pfs48/45 and Pfs230 have research has focused largely on this species. An improved comprehension of this organism's biology is critical to identifying antigenic protein candidates that occur during different stages of its complex lifecycle, including its interactions with the mosquito biological vector and the human host.…”