Expression, purification, crystallization and preliminary X-ray analysis of the sexual stage-specific protein Pfg27 from Plasmodium falciparum

The differentiation and development of sexual stages in Plasmodium falciparum is a complex process which involves the expression of several sexual stage-specific proteins. Pfg27 is one of the most crucial proteins and is expressed abundantly at the onset of gametocytogenesis. An expression and purification system for Pfg27 has been established that yields ∼5 mg l⁻¹ of purified protein in a soluble form. This protein has been crystallized by the hanging-drop vapour-diffusion method using PEG 8000 as a precipitant. The original crystal size was improved significantly by the addition of glucose to the reservoir solution. Pfg27 crystals belong to the space group C222₁, with unit-cell parameters a = 58.9, b = 113.2, c = 91.6 Å. Native diffraction data were collected under cryogenic conditions and phase resolution by a selenomethionine-aided multiple-wavelength anomalous dispersion technique is in progress. The Pfg27 structure will provide a framework for functional and biochemical studies aimed at understanding gametocyte development in P. falciparum.