Functional expression on bacteriophage of the mustard trypsin inhibitor MTI-2

The mustard trypsin inhibitor MTI-2 is a potential tool in the study of interactions between pest insects and plants. It can be applied to study the adaptations of digestive proteases in pest insects. Phage display allows a rapid and exhaustive system for the selection of heterologous protein variants with novel specificities. Here we describe a bacteriophage expression system which permits functional expression of MTI-2 variants. Active and inactive mutants of MTI-2 are constructed and displayed on phage. These are used to demonstrate that an active variant can be selected from a background of 10,000 inactive mutants in four rounds of selection and amplification.