An in vitro polysome display system for identifying ligands from very large peptide libraries

Area of Science:

• Biochemistry
• Molecular Biology
• Synthetic Biology

Background:

• Current peptide display systems have limitations in library size and screening capacity.
• Developing novel methods for large-scale peptide library construction and screening is crucial for drug discovery and protein engineering.

Purpose of the Study:

• To establish a highly efficient in vitro system for constructing and screening massive peptide libraries.
• To identify peptides with high binding affinity to a specific target using a novel polysome display approach.

Main Methods:

• Utilized an in vitro protein synthesis system with Escherichia coli S30 coupled transcription/translation to generate a library of 10(12) random decapeptides.
• Employed polysome isolation and affinity selection using an immobilized monoclonal antibody against dynorphin B.
• Recovered mRNA, converted to cDNA, amplified via polymerase chain reaction (PCR), and cloned into a filamentous phagemid vector for analysis.

Main Results:

• Achieved specific binding of synthesized peptides to the target antibody after four rounds of selection.
• Identified a consensus sequence similar to the known antibody epitope among the selected peptides.
• Determined binding affinities for synthetic peptides ranging from 7 to 140 nM, indicating high specificity.

Conclusions:

• The developed in vitro system enables the screening of peptide libraries significantly larger than existing biological display systems.
• This method offers a powerful platform for rapid identification of high-affinity peptides for various applications.
• The system has the potential to revolutionize peptide discovery and engineering processes.