Figure 2

Library construction and affinity selection of MS2 VLPs. When expressed from a plasmid in bacteria, the coat protein of bacteriophage MS2 forms a virus-like particle (VLP), which we have adapted for peptide display and affinity-selection. A complex library of random peptide sequences is constructed at the level of plasmid DNA. When the DNA is expressed in E. coli, a library of corresponding VLPs is produced, as the recombinant coat proteins self-assemble into VLPs, each of which displays a different guest peptide on its surface and encapsidates its own mRNA. These VLPs are subjected to affinity selection with a specific mAb. Unbound VLPs are washed and discarded. VLPs which display a peptide with an affinity for the mAb used are eluted, and subjected to RT-PCR to generate cDNA for another round of affinity selection. After affinity selection, the VLPs were characterized to determine the sequence of the peptide.