IDENTIFICATION, QUANTITATION AND PURIFICATION OF INSECTICIDAL PROTEINS FROM BACILLUS THURINGIENSIS

摘要

A process for identifying proteinaceous protoxins expressed by Bacillus thuringiensis genes is disclosed. According to the process, daughter toxins are first generated by subjecting a protoxin-containing material, such as parasporal crystals of Bacillus thuringiensis, to limited proteolysis with a proteolytic enzyme in an aqueous suspension having a pH above 9.5. The daughter toxins are then separated by high performance anion-exchange liquid chromatography at a constant pH in excess of 10 in an increasing gradient of a salt, preferably sodium chloride. The gradient conditions, which are specific for the column used, are achieved by employing a series of buffers having increasing concentration of the salt and introduced at a predetermined time and rate. The procedure provides a chromatogram showing clearly identifiable peaks of toxins and permits therefore the qualitative and quantitative characterization of the original mixture and isolation of the individual toxins. By this it provides means of screening and testing new Bacillus thuringiensis isolates, both single- and multigene, and monitoring the level of expression of known genes from a known strain. The digestion and isolation conditions permit the production of the toxins in a biologically fully active state.