title: A novel Pfs38 protein complex on the surface of Plasmodium falciparum blood-stage merozoites.
abstract: The Plasmodium genome encodes for a number of 6-Cys proteins that contain a module of six cysteine residues forming three intramolecular disulphide bonds. These proteins have been well characterized at transmission as well as hepatic stages of the parasite life cycle. In the present study, a large complex of 6-Cys proteins: Pfs41, Pfs38 and Pfs12 and three other merozoite surface proteins: Glutamate-rich protein (GLURP), SERA5 and MSP-1 were identified on the Plasmodium falciparum merozoite surface.
  
  
  
  Recombinant 6-cys proteins i.e. Pfs38, Pfs12, Pfs41 as well as PfMSP-165were expressed and purified using Escherichia coli expression system and antibodies were raised against each of these proteins. These antibodies were used to immunoprecipitate the native proteins and their associated partners from parasite lysate. ELISA, Far western, surface plasmon resonance and glycerol density gradient fractionation were carried out to confirm the respective interactions. Furthermore, erythrocyte binding assay with 6-cys proteins were undertaken to find out their possible role in host-parasite infection and seropositivity was assessed using Indian and Liberian sera.
  
  
  
  Immunoprecipitation of parasite-derived polypeptides, followed by LC-MS/MS analysis, identified a large Pfs38 complex comprising of 6-cys proteins: Pfs41, Pfs38, Pfs12 and other merozoite surface proteins: GLURP, SERA5 and MSP-1. The existence of such a complex was further corroborated by several protein-protein interaction tools, co-localization and co-sedimentation analysis. Pfs38 protein of Pfs38 complex binds to host red blood cells (RBCs) directly via glycophorin A as a receptor. Seroprevalence analysis showed that of the six antigens, prevalence varied from 40 to 99%, being generally highest for MSP-165and GLURP proteins.
  
  
  
  Together the data show the presence of a large Pfs38 protein-associated complex on the parasite surface which is involved in RBC binding. These results highlight the complex molecular interactions among the P. falciparum merozoite surface proteins and advocate the development of a multi-sub-unit malaria vaccine based on some of these protein complexes on merozoite surface.
authors.affiliation: Malaria Group, International Centre for Genetic Engineering and Biotechnology (ICGEB), New Delhi, India.
authors.forename: Gourab
authors.initials: G
authors.lastname: Paul
authors.affiliation: Malaria Group, International Centre for Genetic Engineering and Biotechnology (ICGEB), New Delhi, India.
authors.forename: Arunaditya
authors.initials: A
authors.lastname: Deshmukh
authors.affiliation: Malaria Group, International Centre for Genetic Engineering and Biotechnology (ICGEB), New Delhi, India.
authors.forename: Inderjeet
authors.initials: I
authors.lastname: Kaur
authors.affiliation: Department of Biotechnology, All India Institute of Medical Sciences, New Delhi, India.
authors.forename: Sumit
authors.initials: S
authors.lastname: Rathore
authors.affiliation: Malaria Group, International Centre for Genetic Engineering and Biotechnology (ICGEB), New Delhi, India.
authors.forename: Surbhi
authors.initials: S
authors.lastname: Dabral
authors.affiliation: Department of Microbiology, All India Institute of Medical Sciences, New Delhi, India.
authors.forename: Ashutosh
authors.initials: A
authors.lastname: Panda
authors.affiliation: Department of Clinical Biochemistry, Immunology and Genetics, Statens Serum Institute, Copenhagen, Denmark.|Centre for Medical Parasitology at Department of International Health, Immunology and Microbiology, University of Copenhagen, Copenhagen, Denmark.|Department of Infectious Diseases, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark.
authors.forename: Susheel Kumar
authors.initials: SK
authors.lastname: Singh
authors.affiliation: Malaria Group, International Centre for Genetic Engineering and Biotechnology (ICGEB), New Delhi, India.
authors.forename: Asif
authors.initials: A
authors.lastname: Mohmmed
authors.affiliation: Department of Clinical Biochemistry, Immunology and Genetics, Statens Serum Institute, Copenhagen, Denmark.|Centre for Medical Parasitology at Department of International Health, Immunology and Microbiology, University of Copenhagen, Copenhagen, Denmark.|Department of Infectious Diseases, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark.
authors.forename: Michael
authors.initials: M
authors.lastname: Theisen
authors.affiliation: Malaria Group, International Centre for Genetic Engineering and Biotechnology (ICGEB), New Delhi, India. pawanmal@gmail.com.
authors.forename: Pawan
authors.initials: P
authors.lastname: Malhotra
mesh_terms: D000913:Antibodies, Protozoan / Q000097:blood; D000953:Antigens, Protozoan / Q000032:analysis* / Q000235:genetics / Q000276:immunology; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D006801:Humans; D007194:India; D007988:Liberia; D008565:Membrane Proteins / Q000032:analysis* / Q000235:genetics / Q000276:immunology; D052940:Merozoites / Q000737:chemistry* / Q000276:immunology; D010963:Plasmodium falciparum / Q000737:chemistry* / Q000276:immunology; D025941:Protein Interaction Mapping; D055503:Protein Multimerization; D015800:Protozoan Proteins / Q000032:analysis* / Q000235:genetics / Q000276:immunology; D011994:Recombinant Proteins / Q000235:genetics / Q000276:immunology; D016036:Seroepidemiologic Studies
chemical_list: D000913:Antibodies, Protozoan; D000953:Antigens, Protozoan; D008565:Membrane Proteins; D015800:Protozoan Proteins; D011994:Recombinant Proteins
keywords: 6-cys proteins; Glycophorin A; MSP-165; Plasmodium falciparum