Affinage · Plasmodium

PF3D7_1123600

RAP protein, putative

Audit flag: identity unverified
Annotated
2026-09-08
42 papers in source corpus 11 papers cited in narrative 11 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

PF3D7_1123600 (RAP-1) is a rhoptry bulb protein of Plasmodium falciparum that serves as the organizing core of low-molecular-weight rhoptry protein complexes and acts post-invasion to support intra-erythrocytic parasite development (PMID:17553576, PMID:28205319). It is synthesized as an ~84–86 kDa precursor bearing a cleavable N-terminal signal peptide and is trafficked to the rhoptries via the secretory pathway: processing of the 86-kDa precursor to the mature p82 form is reversibly blocked by brefeldin A and low temperature and irreversibly blocked by N-ethylmaleimide, indicating dependence on Golgi-associated vesicular fusion (PMID:8719244). Within the rhoptries the precursor undergoes two sequential N-terminal cleavages, first a rapid conversion to p82 and then a delayed conversion to p67, and the precursor can assemble with the RAP-2 and RAP-3 products before processing (PMID:9574915). RAP-1 is the core component of the RAP1/2 and RAP1/3 complexes and is enriched in detergent-resistant membranes of schizonts (PMID:17553576). RAP-1 and RAP-2, but not RAP-3, bind the surface of normal erythrocytes, and disruption of RAP-1 abolishes the parasite's ability to tag bystander erythrocytes with rhoptry-derived material (PMID:17624849). The RAP complex is dispensable for rhoptry morphology and erythrocyte invasion but is required for normal parasitophorous vacuolar membrane structure and for intra-erythrocytic growth; conditional knockdown produces altered PVM ultrastructure, delayed growth, and reduced parasitaemia in mice (PMID:28205319). In P. berghei, RAP-1 is required to target RAP-2 to the rhoptries and contributes to virulence, as RAP1-deficient parasites show reduced lethality (PMID:29307564). Monoclonal antibodies against RAP-1 epitopes inhibit parasite growth and invasion in vitro (PMID:2200961, PMID:1279419, PMID:9423886).

Mechanistic history

Synthesis pass · year-by-year structured walk · 11 steps
  1. 1990 Medium

    Established RAP-1 as a rhoptry antigen and defined its biochemical character, answering whether it is a single molecule or a processed multi-component antigen and whether it is a plausible growth-inhibition target.

    Evidence Immunoaffinity purification, SDS-PAGE, autocatalytic processing analysis and monoclonal antibody growth inhibition in P. falciparum

    PMID:2200961

    Open questions at the time
    • Precursor size and trafficking route not yet resolved
    • Molecular function of the protein not defined
    • Relationship of the multiple bands to a defined processing pathway unclear
  2. 1992 Medium

    Mapped inhibitory antibody epitopes relative to the p80-to-p65 cleavage site and linked p65 generation to merozoite release rather than invasion, connecting processing to the parasite life-cycle stage.

    Evidence Epitope mapping with fusion proteins and synthetic peptides plus growth inhibition in P. falciparum

    PMID:1279419

    Open questions at the time
    • Enzyme responsible for cleavage not identified
    • Functional consequence of processing for the protein's activity unknown
  3. 1992 Medium

    Resolved whether metalloproteinases co-purifying with the RAP-1 complex were parasite-derived, ruling them out as bona fide RAP-1 partners.

    Evidence Co-isolation, proteinase inhibitor profiling, immunoprecipitation and immunofluorescence in P. falciparum

    PMID:1477099

    Open questions at the time
    • Does not identify authentic parasite-derived interactors of RAP-1
  4. 1995 High

    Defined the trafficking route of RAP-1, showing precursor-to-mature processing depends on the secretory pathway and Golgi-associated vesicle fusion.

    Evidence Brefeldin A, low-temperature and N-ethylmaleimide blockade with in vitro translation and immunoblot in P. falciparum

    PMID:8719244

    Open questions at the time
    • Identity of the inferred post-translational modification not determined
    • Protease(s) mediating rhoptry processing unknown
  5. 1998 High

    Established the ordered two-step processing pathway (Pr86 to p82 to p67) and showed precursor assembly with RAP-2 and RAP-3 products precedes processing, defining when complexes form.

    Evidence Epitope-selective immunoblot, BFA pulse-chase co-fractionation and immunofluorescence in P. falciparum

    PMID:9574915

    Open questions at the time
    • Functional role of p67-specific window during invasion not directly tested
    • Stoichiometry of the RAP complexes unresolved
  6. 1998 Medium

    Identified a second inhibitory epitope near the p67 N-terminus, extending the map of functionally important, antibody-accessible regions of RAP-1.

    Evidence Owl monkey infection, monoclonal antibody 1D6, in vitro invasion inhibition and peptide mapping in P. falciparum

    PMID:9423886

    Open questions at the time
    • Mechanism by which antibody binding inhibits invasion not defined
    • Native function of the iB-2 region unknown
  7. 2007 Medium

    Positioned RAP-1 as the core of the RAP1/2 and RAP1/3 complexes and localized it to detergent-resistant membranes, framing its role as a scaffolding/complex-organizing component.

    Evidence Detergent-resistant membrane purification, blue native PAGE and mass spectrometry in P. falciparum schizonts

    PMID:17553576

    Open questions at the time
    • Composition of the larger high-molecular-weight species not identified
    • Molecular basis of DRM association unknown
  8. 2007 High

    Used gene disruption to demonstrate RAP-1 is required for transfer of rhoptry-derived protein onto bystander erythrocyte surfaces, assigning a specific function distinct from RAP-3.

    Evidence RAP-1 and RAP-3 knockouts with surface iodination and erythrocyte binding assays in P. falciparum

    PMID:17624849

    Open questions at the time
    • Biological purpose of tagging bystander erythrocytes not established
    • Direct receptor on the erythrocyte surface not identified
  9. 2010 Low

    Placed RAP-1 within the MSP-1 merozoite surface complex, indicating a stage-restricted association that is shed before the ring stage.

    Evidence Antibody pull-down from merozoite lysate with tandem mass spectrometry in P. falciparum

    PMID:21175202

    Open questions at the time
    • Single pull-down/MS without reciprocal validation specific to RAP-1
    • Direct versus indirect nature of the MSP-1 association unresolved
  10. 2017 High

    Defined the essential post-invasion role of the RAP complex, showing RAP-1 is dispensable for invasion but required for PVM integrity and intra-erythrocytic growth.

    Evidence Conditional knockdown with PVM electron microscopy, growth assays and mouse infection in P. falciparum and P. berghei ANKA

    PMID:28205319

    Open questions at the time
    • Molecular mechanism by which RAP complex supports PVM structure unknown
    • Direct RAP-1 contribution versus whole-complex effect not separated
  11. 2018 Medium

    Showed in a rodent model that RAP-1 targets RAP-2 to the rhoptries and contributes to virulence, linking complex assembly to disease outcome.

    Evidence Genetic disruption of RAP1 in P. berghei ANKA with parasitemia and survival measurements

    PMID:29307564

    Open questions at the time
    • Whether RAP-1 targets RAP-2 identically in P. falciparum not tested here
    • Mechanism connecting RAP-2 mislocalization to virulence undefined

Open questions

Synthesis pass · forward-looking unresolved questions
  • The biochemical/molecular activity of RAP-1 itself and the mechanism by which the RAP complex maintains PVM integrity remain unresolved.
  • No defined enzymatic or ligand-binding activity for RAP-1
  • Protease(s) mediating rhoptry processing not identified
  • Mechanistic basis of PVM defect in RAP-deficient parasites unknown

Mechanism profile

Synthesis pass · controlled-vocabulary classification
Partners
PFMSP-1RAP-2RAP-3
Complex memberships
MSP-1 merozoite surface complex (RAP-1 associated)RAP1/2 rhoptry complexRAP1/3 rhoptry complex

Evidence

Reading pass · 11 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
1990 RAP-1 is a rhoptry-localized antigen of P. falciparum consisting of multiple protein components (80, 65, 42, 40 kDa major and 77, 70 kDa minor) derived from the same precursor, is lipophilic, contains disulfide bonds important for its structure, and monoclonal antibodies against it inhibit parasite growth in vitro. Immunoaffinity purification, SDS-PAGE, Western blot, autocatalytic processing analysis, monoclonal antibody inhibition assays, gene sequencing Molecular and biochemical parasitology Medium 2200961
1992 Inhibitory monoclonal antibodies against RAP-1 recognize linear epitopes mapping 10-20 amino acids C-terminal to the proteolytic cleavage site (at amino acid 190) that converts the 80-kDa form (p80) to the 65-kDa form (p65). The 65-kDa processing product is absent from purified merozoites, suggesting its generation is associated with merozoite release rather than erythrocyte invasion. Epitope mapping with beta-galactosidase fusion proteins and synthetic peptides, Western blot, in vitro parasite growth inhibition assay Molecular and biochemical parasitology Medium 1279419
1995 Transport of RAP-1 to the rhoptries is regulated by the secretory pathway. Brefeldin A (BFA) and low temperature reversibly block processing of an 86-kDa precursor (Pr86) to the mature 82-kDa RAP-1 product (p82). N-ethylmaleimide (which prevents vesicle-Golgi fusion) irreversibly blocks this processing. In vitro translation reveals a cleavable N-terminal signal peptide and an initial 84-kDa primary translation product, suggesting RAP-1 acquires an undetected protein modification during maturation. Brefeldin A and low-temperature blockade experiments on intact cells, N-ethylmaleimide treatment, in vitro translation, immunoblot Molecular and biochemical parasitology High 8719244
1998 RAP-1 precursor Pr86 undergoes two sequential N-terminal cleavages: first to p82 (rapid, in rhoptries) then to p67 (delayed, also in rhoptries). Pr86 can form complexes with RAP-2 product p39 and RAP-3 product p37 prior to processing. p82 and p67 are the major RAP-1 forms in purified merozoites but are not relocalized to the merozoite surface under conditions that promote AMA-1 relocalization. Since p67 is absent from ring-stage parasites, it may play a role in a narrow window during merozoite invasion. Immunoblot with epitope-selective antibodies, size fractionation of BFA-treated radiolabeled parasites, immunofluorescence localization Molecular and biochemical parasitology High 9574915
1998 A second inhibitory B-cell epitope (iB-2) was identified in RAP-1 near the amino terminus of p67, distinct from the previously characterized iB-1 (N200TLTPLEELYPT211). Monoclonal antibody 1D6 binds iB-2 and inhibits parasite invasion of erythrocytes in vitro. Anti-iB-1 antibodies were produced during infection but not readily boosted upon reinfection, suggesting iB-1 is immunogenic but not immunodominant. Owl monkey infection model, monoclonal antibody production, in vitro erythrocyte invasion inhibition assay, peptide epitope mapping Infection and immunity Medium 9423886
2007 RAP-1 is the core component of two low-molecular-weight rhoptry complexes (RAP1/2 and RAP1/3) and is enriched in detergent-resistant membranes (DRMs) of P. falciparum schizonts. RAP-1 predominates in high-molecular-weight species by blue native PAGE, suggesting its participation in complexes larger than anticipated. Detergent-resistant membrane purification, blue native PAGE, mass spectrometry Molecular and biochemical parasitology Medium 17553576
2007 RAP-1 and RAP-2 (but not RAP-3) bind to the surface of normal (non-parasitized) erythrocytes. Parasites with RAP-1 gene disruption lose their capacity to tag erythrocytes with rhoptry-derived proteins, implicating RAP-1 in the transfer of rhoptry material to bystander erythrocytes. Gene disruption (RAP-1 and RAP-3 knock-out mutants), surface iodination experiments, binding assays with normal erythrocytes The Journal of infectious diseases High 17624849
2010 RAP-1 is pulled down as part of the PfMSP-1 surface complex on merozoites, together with RAP-2 and two RAP-domain-containing proteins; this complex is present at the schizont/merozoite stage but not in the subsequent ring stage and is shed into culture supernatant. Antibody pull-down from merozoite lysate, tandem mass spectrometry identification Journal of proteome research Low 21175202
2017 The RAP complex (including RAP-1) is not required for rhoptry morphology or erythrocyte invasion, but is required post-invasion for normal parasitophorous vacuolar membrane (PVM) structure and intra-erythrocytic parasite growth. Conditional knockdown of RAP complex members leads to altered PVM structure, delayed intra-erythrocytic growth, and reduced parasitaemias in infected mice. Conditional knockdown (inducible system), electron microscopy of PVM structure, parasite growth assays, mouse infection model Cellular microbiology High 28205319
2018 In P. berghei, RAP-1 is required for targeting of RAP-2 to the rhoptries. RAP1-deficient P. berghei ANKA parasites show increased parasitemia during early infection but reduced virulence (mice survive longer), establishing RAP-1 as a contributor to parasite virulence. Genetic disruption of RAP1 in P. berghei ANKA, mouse infection experiments measuring parasitemia and survival Experimental parasitology Medium 29307564
1992 Three matrix metalloproteinases (220, 95, and 70 kDa) co-isolate with the RAP-1 complex by immunoaffinity chromatography but originate from human serum used to cultivate P. falciparum in vitro (not from the parasite itself), as confirmed by the absence of immunofluorescence staining of intracellular parasites with metalloproteinase-specific antisera. Co-isolation by immunoaffinity chromatography, proteinase inhibitor profiling, immunoprecipitation with monospecific antisera, indirect immunofluorescence Biochimica et biophysica acta Medium 1477099

Source papers

Stage 0 corpus · 42 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
1994 Differential localization of full-length and processed forms of PF83/AMA-1 an apical membrane antigen of Plasmodium falciparum merozoites. Molecular and biochemical parasitology 229 7838184
1998 Genetic polymorphism and natural selection in the malaria parasite Plasmodium falciparum. Genetics 213 9584096
1990 A rhoptry antigen of Plasmodium falciparum is protective in Saimiri monkeys. Parasitology 92 2263413
1990 Characterisation and sequence of a protective rhoptry antigen from Plasmodium falciparum. Molecular and biochemical parasitology 90 2200961
2007 Identification of protein complexes in detergent-resistant membranes of Plasmodium falciparum schizonts. Molecular and biochemical parasitology 73 17553576
2000 Human genetic factors related to susceptibility to mild malaria in Gabon. Genes and immunity 65 11196674
2001 Limonene arrests parasite development and inhibits isoprenylation of proteins in Plasmodium falciparum. Antimicrobial agents and chemotherapy 55 11502528
1992 Inhibitory monoclonal antibodies recognise epitopes adjacent to a proteolytic cleavage site on the RAP-1 protein of Plasmodium falciparum. Molecular and biochemical parasitology 55 1279419
2010 Multiple antigen peptide vaccines against Plasmodium falciparum malaria. Infection and immunity 51 20823210
1995 The secretary pathway of plasmodium falciparum regulates transport of p82/RAP1 to the rhoptries. Molecular and biochemical parasitology 40 8719244
1998 Analysis of the processing of Plasmodium falciparum rhoptry-associated protein 1 and localization of Pr86 to schizont rhoptries and p67 to free merozoites. Molecular and biochemical parasitology 34 9574915
1998 Analysis of inhibitory epitopes in the Plasmodium falciparum rhoptry protein RAP-1 including identification of a second inhibitory epitope. Infection and immunity 33 9423886
1997 Assessment of the humoral immune response against Plasmodium falciparum rhoptry-associated proteins 1 and 2. Infection and immunity 33 9169771
2002 Plasmodium falciparum MAEBL is a unique member of the ebl family. Molecular and biochemical parasitology 32 12076768
2010 Proteome analysis reveals a large merozoite surface protein-1 associated complex on the Plasmodium falciparum merozoite surface. Journal of proteome research 31 21175202
1999 Immune responses against Plasmodium falciparum asexual blood-stage antigens and disease susceptibility in Gabonese and Cameroonian children. The American journal of tropical medicine and hygiene 31 10497996
2017 The Plasmodium rhoptry associated protein complex is important for parasitophorous vacuole membrane structure and intraerythrocytic parasite growth. Cellular microbiology 30 28205319
2007 Members of the low-molecular-mass rhoptry protein complex of Plasmodium falciparum bind to the surface of normal erythrocytes. The Journal of infectious diseases 30 17624849
1993 Specific T-cell recognition of the merozoite proteins rhoptry-associated protein 1 and erythrocyte-binding antigen 1 of Plasmodium falciparum. Infection and immunity 30 8418048
1993 Tumour necrosis factor and interleukin-6 production induced by components associated with merozoite proteins of Plasmodium falciparum. Parasite immunology 30 8506119
2009 Mechanisms of malarial anaemia: potential involvement of the Plasmodium falciparum low molecular weight rhoptry-associated proteins. Acta tropica 27 19695213
1999 IgG reactivities against recombinant Rhoptry-Associated Protein-1 (rRAP-1) are associated with mixed Plasmodium infections and protection against disease in Tanzanian children. Parasitology 25 10581610
2017 PhenoPlasm: a database of disruption phenotypes for malaria parasite genes. Wellcome open research 24 28748223
2003 Does infection with Human Immunodeficiency Virus affect the antibody responses to Plasmodium falciparum antigenic determinants in asymptomatic pregnant women? The Journal of infection 23 12643865
2010 Evidence for negative selection on the gene encoding rhoptry-associated protein 1 (RAP-1) in Plasmodium spp. Infection, genetics and evolution : journal of molecular epidemiology and evolutionary genetics in infectious diseases 22 20363375
1997 Antibody responses to Rhoptry-Associated Protein-1 (RAP-1) of Plasmodium falciparum parasites in humans from areas of different malaria endemicity. Parasite immunology 20 9347514
1996 Limited RAP-1 sequence diversity in field isolates of Plasmodium falciparum. Molecular and biochemical parasitology 19 8784775
1992 Molecular factors responsible for host cell recognition and invasion in Plasmodium falciparum. The Journal of protozoology 19 1560416
1995 Immunogenicity of recombinant Plasmodium falciparum rhoptry associated proteins 1 and 2. Parasite immunology 17 8834763
2001 Rhoptry-associated protein 1-binding monoclonal antibody raised against a heterologous peptide sequence inhibits Plasmodium falciparum growth in vitro. Infection and immunity 16 11254620
2022 Functional genomics of RAP proteins and their role in mitoribosome regulation in Plasmodium falciparum. Nature communications 14 35277503
2009 Limited genetic polymorphism of the Plasmodium vivax low molecular weight rhoptry protein complex in the Colombian population. Infection, genetics and evolution : journal of molecular epidemiology and evolutionary genetics in infectious diseases 14 20026428
2008 Effect of placental malaria and HIV infection on the antibody responses to Plasmodium falciparum in infants. The Journal of infectious diseases 14 18928377
2016 Genetic diversity and natural selection in the rhoptry-associated protein 1 (RAP-1) of recent Plasmodium knowlesi clinical isolates from Malaysia. Malaria journal 12 26847346
1998 A study of antibody and T cell recognition of rhoptry-associated protein-1 (RAP-1) and RAP-2 recombinant proteins and peptides of Plasmodium falciparum in migrants and residents of the state of Rondonia, Brazil. The American journal of tropical medicine and hygiene 12 9715934
2011 Antibodies to the Plasmodium falciparum rhoptry protein RAP-2/RSP-2 in relation to anaemia in Cameroonian children. Parasite immunology 10 21226723
2018 Comparative genomics and proteomic analyses between lethal and nonlethal strains of Plasmodium berghei. Experimental parasitology 8 29307564
1994 Characterization of a new 60 kDa apical protein of Plasmodium falciparum merozoite expressed in late schizogony. Biology of the cell 7 7606209
1992 Towards a malaria vaccine: riding the rollercoaster between unrealistic optimism and lethal pessimism. The Southeast Asian journal of tropical medicine and public health 7 1298072
2010 Conserved regions of the Plasmodium falciparum rhoptry-associated protein 3 mediate specific host-pathogen interactions during invasion of red blood cells. Peptides 4 20833215
2022 Genetic Diversity and Clustering of the Rhoptry Associated Protein-1 of Plasmodium knowlesi from Peninsular Malaysia and Malaysian Borneo. The Korean journal of parasitology 3 36588415
1992 Three matrix metalloproteinases form a non-covalent association with the rhoptry-associated protein-1 of Plasmodium falciparum. Biochimica et biophysica acta 1 1477099