Binding of the 51- and 42-kDa individual components from the Bacillus sphaericus crystal toxin to mosquito larval midgut membranes from Culex and Anopheles sp. (Diptera: Culicidae)

Individual components (P51 and P42) from the crystal toxin (Bin) of Bacillus sphaericus were used for in vitro binding competition experiments with brush border membranes (BBMFs) from Culex pipiens and Anopheles gambiae larval midguts. P51 competed for the Bin binding site with a similar affinity to the Bin toxin, on both BBMFs. For C. pipiens, P42 bound nonspecifically until P51 was added with maximum binding of P42 at a molar ratio of each component. The binding of P42 was much greater on A. gambiae BBMFs and the presence of either P51 or P42 enhanced the binding of the other component, with highest binding when a mole to mole ratio of each protein was supplied.