Peptide screening using PURE ribosome display.

To demonstrate directed protein evolution or selection of functional polypeptides, ribosome display is one of the most ideal technologies of evolutionary engineering. Intrinsic components, such as nucleases in the cell extract-based cell-free protein synthesis systems, reduce the stability of the messenger RNA-ribosome-polypeptide ternary complex, thereby preventing the attainment of reliable results. To overcome this problem, we have developed an effective and highly controllable ribosome display system using the protein synthesizing using recombinant elements (PURE) system. Since the activities of nucleases and other inhibitory factors are very low in the PURE system, the ternary complex is highly stable and the selected mRNA can be reliably recovered. Using this system, we were able to select peptides that specifically bind to monoclonal antibodies from random peptide libraries. The advantages of the modified PURE system for ribosome display strongly substantiate its usability.