title: Export of PfSBP1 to the Plasmodium falciparum Maurer's clefts.
abstract: The human malaria parasite Plasmodium falciparum exports determinants of virulence and pathology to destinations within the host erythrocyte, including the erythrocyte cytoplasm, plasma membrane and membrane profiles of parasite origin termed Maurer's clefts. Most of the exported proteins contain a conserved pentameric motif termed plasmodial export element (PEXEL)/vacuolar transfer signal (VTS) that functions as a cleavable sorting signal permitting export to the host erythrocyte. However, there are some exported proteins, such as the skeleton-binding protein 1 (PfSBP1) that lack the PEXEL/VTS motif and that are not N-terminally processed, suggesting the presence of alternative sorting signals and/or mechanisms. In this study, we have investigated trafficking of PfSBP1 to the Maurer's clefts. Our data show that the transmembrane domain of PfSBP1 functions as an internal signal sequence for entry into the parasite's secretory pathway and for transport to the parasite plasma membrane. Trafficking beyond the parasite's plasma membrane required additional N-terminal domains, which are characterized by a high negative net charge. Biochemical data indicate that these domains affect the solubility and extraction profile, the orientation of the protein within the membrane and the subcellular localization. Our findings suggest new principles of protein export in P. falciparum-infected erythrocytes.
authors.affiliation: Hygiene Institut, Abteilung Parasitologie, Universitätsklinikum Heidelberg, Im Neuenheimer Feld 324, 69120 Heidelberg, Germany.
authors.forename: Theodora
authors.initials: T
authors.lastname: Saridaki
authors.forename: Kathrin S
authors.initials: KS
authors.lastname: Fröhlich
authors.forename: Catherine
authors.initials: C
authors.lastname: Braun-Breton
authors.forename: Michael
authors.initials: M
authors.lastname: Lanzer
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D017353:Gene Deletion; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D010963:Plasmodium falciparum / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D021381:Protein Transport; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D014357:Trypsin / Q000378:metabolism
chemical_list: D002352:Carrier Proteins; C478484:MAHRP-1 protein, Plasmodium falciparum; D008565:Membrane Proteins; C417763:Pfsbp1 protein, Plasmodium falciparum; D015800:Protozoan Proteins; D011994:Recombinant Proteins; D014357:Trypsin