Brefeldin A (BFA) treatment causes retention of GFP–Sys1 at tER sites in an export signal-dependent manner. Parasites coexpressing either GFP–Sys1DxE (WT) or GFP–Sys1AxA (AxA) with (A) mRFP–PfSec12 (from the calmodulin 5′ UTR) or (B) PfSec24a–mRFP were treated with 5 mg ml-1 BFA for 16 h prior to imaging. A merged image of a mock-treated control is shown for comparison. ER-retained GFP–Sys1AxA colocalized with PfSec12 throughout the ER (A), whereas GFP–Sys1DxE was enriched at tER sites coincident with PfSec24a (B). Bar = 5 mm. Lee MC, Moura PA, Miller EA, Fidock DA. Plasmodium falciparum Sec24 marks transitional ER that exports a model cargo via a diacidic motif. Mol Microbiol. 2008