Targeting and processing of nuclear-encoded apicoplast proteins in plastid segregation mutants of Toxoplasma gondii.
The apicoplast is a distinctive organelle associated with apicomplexan parasites, including Plasmodium sp. (which cause malaria) and Toxoplasma gondii (the causative agent of toxoplasmosis). This unusual structure (acquired by the engulfment of an ancestral alga and retention of the algal plastid) is essential for long-term parasite survival. Similar to other endosymbiotic organelles (mitochondria, chloroplasts), the apicoplast contains proteins that are encoded in the nucleus and post-translationally imported. Translocation across the four membranes surrounding the apicoplast is mediated by an N-terminal bipartite targeting sequence. Previous studies have described a recombinant "poison" that blocks plastid segregation during mitosis, producing parasites that lack an apicoplast and siblings containing a gigantic, nonsegregating plastid. To learn more about this remarkable phenomenon, we examined the localization and processing of the protein produced by this construct. Taking advantage of the ability to isolate apicoplast segregation mutants, we also demonstrated that processing of the transit peptide of nuclear-encoded apicoplast proteins requires plastid-associated activity.
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Department of Biology, Cancer Center Flow Cytometry Shared Resource, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
Striepen
B
B
Pletcher
C H
CH
Murray
J M
JM
Roos
D S
DS
D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism*; D002469:Cell Separation; D015500:Chloramphenicol O-Acetyltransferase / Q000378:metabolism; D005434:Flow Cytometry / Q000379:methods*; D005456:Fluorescent Dyes / Q000378:metabolism; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins / Q000378:metabolism; D010957:Plasmids / Q000378:metabolism; D018087:Plastids / Q000235:genetics* / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013347:Subcellular Fractions; D014122:Toxoplasma / Q000235:genetics*; D000097573:Red Fluorescent Protein
D015500:Chloramphenicol O-Acetyltransferase; D005456:Fluorescent Dyes; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins; D011993:Recombinant Fusion Proteins; D000097573:Red Fluorescent Protein