Crystallization and preliminary X-ray diffraction studies of the 51 kDa protein of the mosquito-larvicidal binary toxin from Bacillus sphaericus

Certain strains of Bacillus sphaericus produce a highly toxic mosquito-larv icidal protein during sporulation which is active against vectors of dengue , encephalitis and malaria. This toxin is initially expressed as 51 and 42 kDa proteins and is converted to 43 and 39 kDa proteins, respectively, whic h form the active heterodimer complex. For a better understanding of the to xicity mechanism at the molecular level, the 51 kDa protein of the binary t oxin of B. sphaericus strain 2297 was expressed as a glutathione-S-transfer ase fusion protein and purified by affinity chromatography. Protein crystal s were grown from an amorphous precipitate in five months using the hanging -drop vapor-diffusion method. The protein crystals were dissolved and were found to be composed of a proteolytically modified 45.2 kDa derivative simi lar to the active form of this protein. The crystals form in space group P4 (3)2(1)2 (or P4(1)2(1)2) and diffract to 2.6 Angstrom, with unit-cell dimen sions a = b = 133.48, c = 69.76 Angstrom.