Issue 43, 2014

Cross-strand histidine–aromatic interactions enhance acyl-transfer rates in beta-hairpin peptide catalysts

Abstract

A reactive tagging methodology was used to select the species most reactive to an acylation reagent from a solid phase library of beta hairpin peptides. Hits bearing an electron-rich aromatic residue across strand from a reactive histidine were found to competitively become N-acylated. In addition to displaying rapid N-acylation rates the hit peptide was additionally deacylated in the presence of a nucleophile, thus closing a putative catalytic cycle. Variants of the hit peptide were studied to elucidate both the magnitude (up to 18 000-fold over background, kcat/kuncat = 94 000 000, or 45-fold over Boc-histidine methyl ester) and mechanism of acyl transfer catalysis. A combination of CH–π, cation–π and HisH+–O interactions in the cationic imidazole transition state is implicated in the rate acceleration, in addition to the fidelity of the beta hairpin fold. Moreover, NMR structural data on key intermediates or models thereof suggest that a key feature of this catalyst is the ability to access several different stabilizing conformations along the catalysis reaction coordinate.

Graphical abstract: Cross-strand histidine–aromatic interactions enhance acyl-transfer rates in beta-hairpin peptide catalysts

Supplementary files

Article information

Article type
Paper
Submitted
15 Aug. 2014
Accepted
10 Sept. 2014
First published
11 Sept. 2014

Org. Biomol. Chem., 2014,12, 8711-8718

Author version available

Cross-strand histidine–aromatic interactions enhance acyl-transfer rates in beta-hairpin peptide catalysts

M. Matsumoto, S. J. Lee, M. R. Gagné and M. L. Waters, Org. Biomol. Chem., 2014, 12, 8711 DOI: 10.1039/C4OB01754D

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