Abstract:
Cyclic peptides possess unique properties, such as a small molecular weight, high
binding affinity and specificity, and ease of synthesis and modification, that make
them ideal for the development of novel therapeutic molecules. Indeed, in the last
decade, an increasing number of peptide-based drugs have been approved by the US
Food and Drug Administration. To accelerate the discovery of cyclic peptide-based
binders, we recently developed a combinatorial technology. In this project, we
assessed the efficacy of our novel platform to rapidly isolate cyclic peptide inhibitors
of a serine protease. The identity of selected peptides was initially revealed by DNA
sequencing and the binding affinities readily determined using recombinantly
expressed peptide fusions. Best cyclic peptide inhibitors were further chemically
synthesized via solid phase peptide synthesis. Peptide cyclisation was achieved
through cysteine oxidation using a buffer containing DMSO. Next, cyclic peptides
were purified by RP HPLC and their molecular weights assessed by mass
spectrometry. Finally, the inhibitory potency of isolated peptides was determined
using a colorimetric assay. Best isolated cyclic peptide inhibitor showed picomolar
inhibitory activity and affinity.
