Colocalization studies of RALP1 with rhoptry and microneme marker proteins. (A and B) RALP1-C-specific antibodies (green) colocalize with the rhoptry protein RAP1 (red) (A) and predominantly colocalize with CLAG9 a rhoptry-specific marker, (red) (B) in fixed schizonts (s) and free merozoites (m) using RAP1- and CLAG9-specific antibodies, respectively. (C and D) RALP1-C-specific antibodies (green) visualize a different compartment within the parasite than the microneme marker proteins EBA-175 (red) (C) and EBA-181 (red) (D), as is evident in the merge of the two fluorescence photomicrographs. Nuclei were stained blue (DAPI).Haase S, Cabrera A, Langer C, Treeck M, Struck N, Herrmann S, Jansen PW, Bruchhaus I, Bachmann A, Dias S, Cowman AF, Stunnenberg HG, Spielmann T, Gilberger TW. Characterization of a conserved rhoptry-associated leucine zipper-like protein in the malaria parasite Plasmodium falciparum. Infect Immun. 2008 76:879-87.

ARO is late transcribed in blood stages of Plasmodium falciparum and co-localizes with the rhoptries. Co-localization of PfARO with (upper panel) the rhoptry marker RALP-1 (red) and (lower panel) the microneme marker EBA-181 (red). Nuclei stained with DAPI (blue). Enlargement of selected areas are marked with white square and referred as Zoom. Scale bar, 1 μm. Colocalization with the rhoptry bulb marker RALP-1 and the microneme marker EBA-181 identify PfARO as a rhoptry protein.Cabrera A, Herrmann S, Warszta D, Santos JM, John Peter AT, Kono M, Debrouver S, Jacobs T, Spielmann T, Ungermann C, Soldati-Favre D, Gilberger TW. Dissection of minimal sequence requirements for rhoptry membrane targeting in the malariaparasite. Traffic. 2012 13(10):1335-50. PMID:

Localization of RALP1 in P. falciparum merozoites. RALP1 localization shown by an immunofluorescence assay. Paraformaldehyde-fixed mature schizonts were probed with rabbit anti-RALP1-C2 (green; C-terminal region of RALP1, encompassing 315 aa [N396 to K710]) and mouse anti-RAP1 (rhoptry bulb marker) antibodies (top) or anti-RON4 (rhoptry neck marker) (middle) or anti-RALP1-N1 (bottom; red; C-terminal region of RALP1, encompassing 239 aa [N396 to P634]) antibody. Parasite nuclei were stained with DAPI (blue). Scale bars represent 5 mm. DIC, differential interference contrast. (E) RALP1 localization shown by IEM. Two sections of merozoites in schizont-infected erythrocytes probed with purified rabbit anti-RALP1-C2 antibody and subsequently with a secondary antibody conjugated with gold particles are shown. The black dots indicate signals from gold particles localized in rhoptry necks. R, rhoptry.Ito D, Hasegawa T, Miura K, Yamasaki T, Arumugam TU, Thongkukiatkul A, Takeo S, Takashima E, Sattabongkot J, Han ET, Long CA, Torii M, Tsuboi T. RALP1 is a rhoptry neck erythrocyte-binding protein of Plasmodium falciparum merozoites and a potential blood-stage vaccine candidate antigen. Infect Immun. 2013 81(11):4290-8.