Use of H/D isotope effects to gather information about hydrogen bonding and hydrogen exchange rates
Publication date: Available online 11 October 2013
Source:Journal of Magnetic Resonance
Author(s): Mitsuhiro Takeda , Yohei Miyanoiri , Tsutomu Terauchi , Chin-Jiun Yang , Masatsune Kainosho
Polar side-chains in proteins play important roles in formingand maintaining three-dimensional structures, and thus participate invarious biological functions. Until recently, most protein NMR studieshave focused onthe non-exchangeable protons of amino acid residues.Theexchangeable protons attached to polar groups, such as hydroxyl (OH), sulfhydryl (SH), and amino (NH2)groups,have mostly been ignored, becausein many cases these hydrogen atoms exchange too quickly with water protons, makingNMR observations impractical. However, in certain environments, such as deep within the hydrophobic interior of a protein, or in a strong hydrogen bond to other polar groups or interacting ligands, the protons attached to polar groupsmay exhibit slowhydrogen exchange rates and thus become NMR accessible.To explore the structural and biological implications of the interactions involvingpolar side-chains, we have developed versatile NMR methods to detect suchcases by observing the line shapes of13C-NMR signalsnear the polar groups,which are affected by deuterium-proton isotope shifts in a mixture of H2O and D2O. These methods allow the detection ofpolar side-chains with slow hydrogen-deuterium exchange rates, and therefore provideopportunities to retrieve information about the polar side-chains,whichmightotherwise be overlooked by conventional NMR experiments. Future prospects of applications using deuterium-proton isotope shifts to retrieve missing structural and dynamic information of proteins are discussed.
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