J Biol Chem. 2009 Oct 6. [Epub ahead of print]
Genetic evidence that an endosymbiont-derived ERAD system functions in import of apicoplast proteins
Agrawal S, van Dooren GG, Beatty WL, Striepen B.
University of Georgia, United States;
Most apicomplexan parasites harbor a relict chloroplast, the apicoplast, that is critical for their survival. While the apicoplast maintains a small genome, the bulk of its proteins are nuclear-encoded and imported into the organelle. Several models have been proposed to explain how proteins might cross the four membranes that surround the apicoplast, however experimental data discriminating these models is largely missing. Here we present genetic evidence that apicoplast protein import depends on elements derived from the ER associated protein degradation (ERAD) system of the endosymbiont. We identify two sets of ERAD components in Toxoplasma gondii, one associated with the ER and cytoplasm and one localized to the membranes of the apicoplast. We engineer a conditional null mutant in apicoplast Der1, the putative pore of the apicoplast ERAD complex, and find that loss of Der1Ap results in loss of apicoplast protein import and subsequent death of the parasite.
PMID: 19808683 [PubMed - as supplied by publisher]