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.