A phage-based system to select multiple protein-protein interactions simultaneously from combinatorial libraries

Selectively infective phage (SIP) can be used to identify protein-protein interactions. SIP was modified to facilitate the simultaneous selection of interacting protein pairs from large combinatorial libraries. An interference-resistant phage was constructed which non-covalently, but stably links the genetic information of an interacting pair, encoded separately on phage and phagemid vectors, by co-packaging into heteropolyphages. In a model system, the interaction between a SIP-selected peptide and the intracellular domain of the p75 neurotrophin receptor was detected in the presence of a 10(4)-fold excess of a non-interacting control pair (jun leucine zipper and p75 intracellular domain) via SIP hetero-polyphage transductants. To minimize the redundancy of transductants and to minimize possible ligand exchange generated in a solution-based SIP screening, a filter-based in situ infectivity screening was developed. The combination of the above techniques may provide a powerful system for rapid screening of very large sequence spaces.