Bis-imidazoles as molecular probes for peripheral sites of the zinc endopeptidase of botulinum neurotoxin serotype A
作者:Isidro Merino、Jason D. Thompson、Charles B. Millard、James J. Schmidt、Yuan-Ping Pang
DOI:10.1016/j.bmc.2006.01.015
日期:2006.5
Botulinum neurotoxin serotype A (BoNTA) is highly toxic, and its antidote is currently unavailable. The essential light-chain subunit of BoNTA is a zinc endopeptidase that can be used as a target for developing antidotes. However, the development of high-affinity, small-molecule inhibitors of the endopeptidase is as challenging as the development of small-molecule inhibitors of protein-protein complexation. This is because the polypeptide substrate wraps around the circumference of the endopeptidase upon binding, thereby constituting an unusually large substrate-enzyme interface of 4840 angstrom(2). To overcome the large-interface problem, we propose using the zinc-coordination and bivalence approaches to design inhibitors of BoNTA. Here we report the development of alkylene-linked bis-imidazoles that inhibit the endopeptidase in a two-site binding mode, The bis-imidazole tethered with 13 methylene groups, the most potent of the alkylene-linked dimers, showed 61% inhibition of the zinc endopeptidase of BoNTA at a concentration of 100 mu M. The results demonstrate the presence of a peripheral binding site for an imidazolium group at the rim of the BoNTA active-site cleft. This peripheral site enables the use of the bivalence approach to improve Our previously reported small-molecule inhibitors that were developed according to the zinc-coordination approach. (c) 2006 Elsevier Ltd All rights reserved.