title: Dissection of minimal sequence requirements for rhoptry membrane targeting in the malaria parasite.
abstract: Rhoptries are specialized secretory organelles characteristic of single cell organisms belonging to the clade Apicomplexa. These organelles play a key role in the invasion process of host cells by accumulating and subsequently secreting an unknown number of proteins mediating host cell entry. Despite their essential role, little is known about their biogenesis, components and targeting determinants. Here, we report on a conserved apicomplexan protein termed Armadillo Repeats-Only (ARO) protein that we localized to the cytosolic face of Plasmodium falciparum and Toxoplasma gondii rhoptries. We show that the first 20 N-terminal amino acids are sufficient for rhoptry membrane targeting. This protein relies on both - myristoylation and palmitoylation motifs - for membrane attachment. Although these lipid modifications are essential, they are not sufficient to direct ARO to the rhoptry membranes. Mutational analysis revealed additional residues within the first 20 amino acids of ARO that play an important role for rhoptry membrane attachment: the positively charged residues R9 and K14. Interestingly, the exchange of R9 with a negative charge entirely abolishes membrane attachment, whereas the exchange of K14 (and to a lesser extent K16) alters only its membrane specificity. Additionally, 17 proteins predicted to be myristoylated and palmitoylated in the first 20 N-terminal amino acids were identified in the genome of the malaria parasite. While most of the corresponding GFP fusion proteins were trafficked to the parasite plasma membrane, two were sorted to the apical organelles. Interestingly, these proteins have a similar motif identified for ARO.
authors: M.G. DeGroote Institute for Infectious Disease Research, Department of Pathology and Molecular Medicine, McMaster University, Hamilton, ON, Canada.
authors: Ana
authors: A
authors: Cabrera
authors: Susann
authors: S
authors: Herrmann
authors: Dominik
authors: D
authors: Warszta
authors: Joana M
authors: JM
authors: Santos
authors: Arun T
authors: AT
authors: John Peter
authors: Maya
authors: M
authors: Kono
authors: Sandra
authors: S
authors: Debrouver
authors: Thomas
authors: T
authors: Jacobs
authors: Tobias
authors: T
authors: Spielmann
authors: Christian
authors: C
authors: Ungermann
authors: Dominique
authors: D
authors: Soldati-Favre
authors: Tim W
authors: TW
authors: Gilberger
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D051186:Armadillo Domain Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D015388:Organelles / Q000737:chemistry / Q000378:metabolism*; D010963:Plasmodium falciparum / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D021381:Protein Transport; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014122:Toxoplasma / Q000378:metabolism*
chemical_list: D051186:Armadillo Domain Proteins; D008565:Membrane Proteins; D015800:Protozoan Proteins