Crystallization of the mosquito-larvicidal binary toxin produced by Bacillus sphaericus

The Bacillus sphaericus binary toxin is expressed during the early stages of sporulation and is composed of two separately encoded polypeptides: BinA (41.9 kDa) and BinB (51.4 kDa). The binary toxin forms microcrystalline inclusions inside the mother cell that, once ingested, are solubilized in the alkaline pH of the larval gut. B. sphaericus cultures were grown to complete sporulation, harvested and washed. The binary toxin was solubilized with 50 mM NaOH, purified using column chromatography and crystallized. Crystals were grown using the sitting-drop vapor-diffusion method in a glycine-buffered solution containing 0.5 M NaCl and 19.5% PEG 4000 as the precipitant. Native data were collected to a resolution of 2.7 A.