Phage display

Phage display is a laboratory technique for the study of protein interactions that uses bacteriophages (viruses that infect bacteria) to produce and "display" the proteins on their surfaces. Since the proteins remain attached to the surface of the phage, it is possible to isolate the phages displaying desirable proteins from among very large collections (libraries) of phages, using e.g. other protein or DNA molecules as baits. The DNA of the selected phages can then be sequenced to establish the identity of selected proteins. The phages themselves can be further propagated in bacteria to amplify or diversify the selected protein library, with potential for conducting directed evolution experiments with multiple rounds of selection and diversification.

Specifically, a gene encoding a protein of interest is inserted into a phage coat protein gene, causing the phage to "display" the protein on its outside while containing the gene for the protein on its inside. This couples the genotype (gene), phenotype (protein) in the context of an organism (phage) capable of replication. The phages displaying proteins of interest can then be selected using other proteins or DNA sequences in order to e.g., identify natural protein binding partners or antibodies with a high binding affinity.

The most common bacteriophages used in phage display are M13 and fdfilamentous phage, though T4, T7, and λ phage have also been used.