Crystallization and preliminary X-ray analysis of the Plasmodium vivax sexual stage 25 kDa protein Pvs25, a transmission-blocking vaccine candidate for malaria

The Plasmodium vivax sexual stage 25 kDa protein Pvs25 is expressed on the surface of the ookinete form of the parasite. Monoclonal antibodies directed against Pvs25 block the development of P. vivax oocysts in the mosquito host. Thus, Pvs25 is a potential vaccine candidate for eliciting transmission-blocking immunity in individuals living in malaria-epidemic regions. Pvs25 which was expressed and purified for clinical trials was crystallized using polyethylene glycol as the precipitating agent and diffracts X-rays to 2.3 Å. The orthorhombic Pvs25 crystal form belongs to space group P2₁2₁2₁, with unit-cell parameters a = 42.6, b = 59.8, c = 66.8 Å and one molecule in the asymmetric unit. Reductively methylated Pvs25 crystallized in two forms: an orthorhombic P2₁2₁2₁ form with unit-cell parameters a = 43.4, b = 62.9, c = 66.9 Å and one molecule in the asymmetric unit and a monoclinic P2₁ form with unit-cell parameters a = 53.5, b = 43.3, c = 65.3 Å, β = 104.0° which was predicted to have one or two molecules in the asymmetric unit. Several native and heavy-atom data sets have been collected from Pvs25 and methylated Pvs25 crystals for use in MAD or MIR techniques.