CRYSTALLIZATION OF A MEMBRANE PORE-FORMING PROTEIN WITH MOSQUITOCIDALACTIVITY FROM BACILLUS-THURINGIENSIS SUBSPECIES KYUSHUENSIS

CytB, a membrane pore-forming toxin from Bacillus thuringiensis subspe cies kyushuensis, is specifically toxic to dipteran insect larvae but broadly cytolytic in vitro. It has been purified in the protoxin form from a recombinant Escherichia coli source and crystals have been obta ined which diffract X-rays to at least 2.6 Angstrom resolution. The te ndency for CytB to aggregate in solution was overcome by including 50 mM of urea or 8 mM of ethanolamine during crystallization. Mutants des igned to add or subtract single cysteine residues for the purpose of h eavy atom derivative preparation were similarly purified and crystalli zed. The crystals are hexagonal bipyramids. They belong to space group P6(1)22 (or P6(5)22) with lattice constants a = b = 67.34 Angstrom, c = 170.96 Angstrom, and contain one molecule of the CytB protoxin (MW 29235) per asymmetric unit and 27% solvent by volume. (C) 1995 Wiley-L iss, Inc.