Serpin Phage Display: The Use of a T7 System to Probe Reactive Center Loop Libraries with Different Serine Proteinases

Phage display is a protein engineering approach that involves construction of libraries of variant proteins displayed on the surface of bacteriophage as capsid fusion proteins and their screening for binding and inhibitory function through the use of bait proteins. Recently, we adapted a commercially available T7 phage display system to create phage-displayed serpin libraries hypervariable in up to five positions in their reactive center loop (RCL). The RCL is a key determinant in serpin specificity, the relationship between the structure of a given serpin and which target proteinase(s) it inhibits. In this chapter, we describe protocols to assess the feasibility of this method for different serpin/proteinase combinations and share experience with this technology gathered in the course of studying two serpins and multiple proteinases with this powerful iterative screening approach.