Rational Improvement of Peptide Affinity to Human

Authors: Hong Liu ShuoFen Dou Xue Zhang Yan Wang QingLi Wen YaNan Mu

Publish Date: 2016/02/18

Volume: 22, Issue: 3, Pages: 371-376

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Abstract

The pregnancyrelated serine protease HtrA3 plays an important role in human placental development and has recently been recognized as a potential therapeutic target in the treatment of cancer Previously a Cterminal pentapeptide FGRWV–COOH was identified to bind at the PDZ domain of HtrA3 with a moderate affinity Here based on the highresolution complex crystal structure of HtrA3 PDZ domain with the pentapeptide ligand we successfully introduced a rationally designed halogen bond to the complex interface by substituting R4hydrogen atom of the indole moiety of peptide Trp1 residue with a halogen atom Highlevel theoretical calculations suggested that bromine is the best choice that can render strong interaction energy for the halogen bond and can confer high affinity to the PDZ–peptide complex Fluorescence spectroscopy characterizations revealed that the resulting R4brominated peptide K d = 015 ± 003 μM exhibited 12fold affinity improvement relative to its nonhalogenated counterpart K d = 18 ± 04 μM In contrast the PDZbinding affinity of R6brominated peptide K d = 12 ± 01 μM a negative control that was unable to form the halogen bond according to theoretical investigations did not change substantially as compared to the nonhalogenated peptide

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