RP-1776, a novel cyclic peptide produced by Streptomyces sp., inhibits the binding of PDGF to the extracellular domain of its receptor

RP-1776, a novel cyclic peptide, was isolated from the culture broth of Streptomyces sp. KY11784. RP-1776 selectively inhibited the binding of PDGF BB to the extracellular domain of the PDGF beta -receptor with an IC50 value of 11 +/-6 muM. Detailed binding experiments suggested that RP-1776 directly interacts with PDGF BB. RP-1776 inhibited the phosphorylation of the PDGF beta -receptor induced by PDGF BB. These results suggested that RP-1776 antagonizes the signaling of PDGF BB probably through the inhibition of PDGF BB binding to the PDGF beta -receptor.