Fusion proteins with both insecticidal and neomycin phosphotransferase II activity

Hybrid proteins consisting of N-terminal fragments of increasing length of a Bacillus thuringiensis insecticidal protein (Bt2) fused to neomycin phosphotransferase II (NPTII) were produced in Escherichia coli. The minimum fragment required for insect toxicity is comprised of the first 607 amino acids of Bt2. Fusion proteins not containing this minimum fragment were non-toxic. The NPTII activity of the different non-toxic hybrid proteins varied considerably but was not correlated with the length of the Bt2 fragment. Fusion proteins including the minimum toxic fragment of Bt2 exhibited insecticidal and NPTII activity comparable to that of the individual proteins. This was largely independent of the fusion point within Bt2. Our data suggest that the conformation of the Bt2 polypeptide exerts an important influence on the enzymatic activity of the fused NPTII protein. The combination of insecticidal activity and a dominant selectable trait into one protein offers important advantages for the generation of insect resistant transgenic plants.