Improving the display of proteins on filamentous phage

In phage display technology, polypeptides are displayed on the surface of filamentous bacteriophage by genetic fusion to a coat protein. However, the fraction of phage particles bearing the fusion protein can be low. Here we found that we could improve the display of a protein (Stoffel fragment of Taq polymerase fused to the p3 protein of the phage) by mutation of the signal sequence and use of helper phage with a protease-cleavable coat protein. Over multiple rounds of infection, proteolysis and binding to an anti- Taq antibody, we were able to select strongly for display of the fusion protein (>50-fold), and for mutations in the translation initiation region and in the signal sequence of the fusion. This suggests a general means of improving the display of proteins on phage.