Pf Sar1p is associated with coated vesicles and Maurer clefts. (A) Western blot analysis of uninfected and IRBCs incubated with AlF demonstrated that Pf Sar1p was an approximate 23-kDa Triton X-100-insoluble, SDS-soluble protein that was absent in uninfected RBCs. IFA showed Pf Sar1p localized to the parasite compartment and structures in the RBC cytosol. Immunoelectron microscopy revealed Pf Sar1p associated with (B) coated vesicles (V), black arrowhead, and (C) Maurer clefts (MC), white arrowhead, within the RBC cytosol. Scale bar = 70 nm.