side chain–side chain hydrogen bonds
Springer Online Journal Archives 1860-2000
Chemistry and Pharmacology
Abstract We describe the direct observation of side chain–side chain hydrogen bonding interactions in proteins with sensitivity-enhanced NMR spectroscopy. Specifically, the remote correlation between the guanidinium nitrogen 15Nε of arginine 71, which serves as the hydrogen donor, and the acceptor carboxylate carbon 13CO2 γ of aspartate 100 in a 12 kDa protein, human FKBP12, is detected via the trans-hydrogen bond 3h J Nε CO2γ coupling by employing a novel HNCO-type experiment, soft CPD-HNCO. The 3h J Nε CO2γ coupling constant appears to be even smaller than the average value of backbone 3h J NC′ couplings, consistent with more extensive local dynamics in protein side chains. The identification of trans-hydrogen bond J-couplings between protein side chains should provide useful markers for monitoring hydrogen bonding interactions that contribute to the stability of protein folds, to alignments within enzyme active sites and to recognition events at macromolecular interfaces.
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