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Interchain Hydrogen-Bonding Interactions may Facilitate Translocation of K+ Ions across the Potassium Channel Selectivity Filter, as Suggested by Synthetic Modeling Chemistry
Juan C. Mareque Rivas, Harald Schwalbe and Stephen J. Lippard
Proceedings of the National Academy of Sciences of the United States of America
Vol. 98, No. 17 (Aug. 14, 2001), pp. 9478-9483
Published by: National Academy of Sciences
Stable URL: http://www.jstor.org/stable/3056377
Page Count: 6
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A 4-fold symmetric arrangement of TVGYG polypeptides forms the selectivity filter of the K+ channel from Streptomyces lividans (KcsA). We report the synthesis and properties of synthetic models for the filter, p-tert-butyl-calixarene-(OCH2CO-XOBz)4 (X = V, VG, VGY), 1-3. The first cation (Na+, K+) binds to the four $-\lbrace\!OCH_2CO\rbrace-$ units, a region devised to mimic the metal-binding site formed by the four T residues in KcsA. NMR studies reveal that cations and valine amide protons compete for the carbonyl oxygen atoms, converting N-HVal···O=C hydrogen bonds to M+···O=C bonds (M+ = Na+ or K+). The strength of these interchain N-HVal···O=C hydrogen bonds varies in the order 3 > 2 > 1. We propose that such interchain H-bonding may destabilize metal binding in the selectivity filter and thus help create the low energy barrier needed for rapid cation translocation.
Proceedings of the National Academy of Sciences of the United States of America © 2001 National Academy of Sciences