A peptide analog of the calmodulin‐binding domain of myosin light chain kinase adopts an aL‐helical structure in aqueous trifluoroethanol

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Abstract
A 22‐residue synthetic peptide encompassing the calmodulin (CaM)‐binding domain of skeletal muscle myosin light chain kinase was studied by two‐dimensional NMR and CD spectroscopy. In water the peptide does not form any regular structure; however, addition of the helix‐inducing solvent trifluoroethanol (TFE) causes it to form an α‐helical structure. The proton NMR spectra of this peptide in 25% and 40% TFE were assigned by double quantum‐filtered J‐correlated spectroscopy, total correlation spectroscopy, and nuclear Overhauser effect correlated spectroscopy spectra. In addition, the α‐carbon chemical shifts were obtained from (1H,13C)‐heteronuclear multiple quantum coherence spectra. The presence of numerous dNN(i, i + 1), dαN( i, i + 3), and d αβ (i, i + 3) NOE crosspeaks indicates that an α ‐helix can be formed from residues 3 to 20; this is further supported by the CD data. Upfield α ‐proton and downfield α ‐carbon shifts in this region of the peptide provide further support for the formation of an α ‐helix. The helix induced by TFE appears to be similar to that formed upon binding of the peptide to CaM.

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