Insect-cell expression, crystallization and X-ray data collection of the bradyzoite-specific antigen BSR4 from Toxoplasma gondii.

Toxoplasma gondii is an important global pathogen that infects nearly one third of the world's adult population. A family of developmentally expressed structurally related surface-glycoprotein adhesins (SRSs) mediate attachment to and are utilized for entry into host cells. The latent bradyzoite form of T. gondii persists for the life of the host and expresses a distinct family of SRS proteins, of which the bradyzoite-specific antigen BSR4 is a prototypical member. Structural studies of BSR4 were initiated by first recombinantly expressing BSR4 in insect cells, which was followed by crystallization and preliminary X-ray data collection to 1.95 A resolution. Data processing showed that BSR4 crystallized with one molecule in the asymmetric unit of the P4(1)2(1)2 or P4(3)2(1)2 space group, with a solvent content of 60% and a corresponding Matthews coefficient of 2.98 A(3) Da(-1).