Disruption of msp7 in P berghei and MSP7 association with MSP1. (A) The msp7-targeting sequence was cut out from the construct pDHΔMSP7 and inserted by double homologous recombination into the msp7 gene. Southern blot analysis of P berghei genomic DNA from WT and MSP7ko parasites, digested with EcoR1 and HindIII, and probed with (lower left) an msp7 probe or (lower center) a Toxoplasma gondii DHFR probe. Northern blot analysis of msp7 expression (lower right) in WT and MSP7ko parasites: RNA was purified from schizonts of WT (left panels) and MSP7ko (right panels) parasites and were hybridized with probes corresponding to msp7 (upper) and a control (lower). (B) Immunoprecipitation analysis detecting MSP7 as a 42-kDa band in extracts of WT parasites, which is absent in the extracts of MSP7ko parasites. In contrast, MSP1 is expressed in both parasite lines. NP-40 extracts of [³⁵S]-biosynthetically labeled WT parasites (lanes 1, 3, 5, 7, and 8) or MSP7ko parasites (lanes 2, 4, and 6) were mixed with rabbit polyclonal anti-P yoelii MSP7 (lanes 1 and 2), monoclonal antibody 25.1 (lanes 3 and 4), mouse polyclonal anti-P yoelii MSP1 (lanes 5 and 6), normal rabbit serum (lane 7), or normal mouse serum (lane 8). Immunoprecipitates were analyzed using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and fluorography. Locations of the 42-kDa MSP7 and the 230-kDa MSP1 bands are indicated by arrows. Mobilities of standard molecular mass markers are indicated. (C) IFA analysis of MSP7 and MSP1 protein expression in WT and MSP7ko parasites. MSP7 was detected by fluorescence in schizonts of the WT parasite but not in schizonts of the MSP7ko parasite. In contrast, MSP1 was detected in WT and MSP7ko parasites.