title: Experimental determination of the membrane topology of the Plasmodium protease Plasmepsin V.
abstract: The malaria parasite exports hundreds of proteins into its host cell. The majority of exported proteins contain a Host-Targeting motif (also known as a Plasmodium export element) that directs them for export. Prior to export, the Host-Targeting motif is cleaved by the endoplasmic reticulum-resident protease Plasmepsin V and the newly generated N-terminus is N-α-acetylated by an unidentified enzyme. The cleaved, N-α-acetylated protein is trafficked to the parasitophorous vacuole, where it is translocated across the vacuole membrane. It is clear that cleavage and N-α-acetylation of the Host-Targeting motif occur at the endoplasmic reticulum, and it has been proposed that Host-Targeting motif cleavage and N-α-acetylation occur either on the luminal or cytosolic side of the endoplasmic reticulum membrane. Here, we use self-associating 'split' fragments of GFP to determine the topology of Plasmepsin V in the endoplasmic reticulum membrane; we show that the catalytic protease domain of Plasmepsin V faces the endoplasmic reticulum lumen. These data support a model in which the Host-Targeting motif is cleaved and N-α-acetylated in the endoplasmic reticulum lumen. Furthermore, these findings suggest that cytosolic N-α-acetyltransferases are unlikely to be candidates for the N-α-acetyltransferase of Host-Targeting motif-containing exported proteins.
authors: Institute of Structural and Molecular Biology, Division of Biosciences, Birkbeck and University College London, London, United Kingdom.
authors: Sarah J
authors: SJ
authors: Tarr
authors: Institute of Structural and Molecular Biology, Division of Biosciences, Birkbeck and University College London, London, United Kingdom.
authors: Andrew R
authors: AR
authors: Osborne
mesh_terms: D000107:Acetylation; D020816:Amino Acid Motifs; D016282:Aspartic Acid Endopeptidases / Q000235:genetics / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000201:enzymology* / Q000235:genetics; D007425:Intracellular Membranes / Q000201:enzymology*; D010963:Plasmodium falciparum / Q000201:enzymology* / Q000235:genetics; D021381:Protein Transport / Q000502:physiology; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism*; D014617:Vacuoles / Q000201:enzymology* / Q000235:genetics
chemical_list: D015800:Protozoan Proteins; D016282:Aspartic Acid Endopeptidases; C089643:plasmepsin