Abstract
Ion mobility measurements and molecular dynamic simulations have been performed for a series of peptides designed to have helix-turn-helix motifs. For peptides with two helical sections linked by a short loop region: AcA14KG3A14K+2H+, AcA14KG5A14K+2H+, AcA14KG7A14K+2H+, and AcA14KSar3A14K+2H+ (Ac = acetyl, A = alanine, G = glycine, Sar = sarcosine and K = lysine); a coiled-coil geometry with two anti-parallel helices is the lowest energy conformation. The helices uncouple and the coiled-coil unfolds as the temperature is raised. Equilibrium constants determined as a function of temperature yield enthalpy and entropy changes for the unfolding of the coiled-coil. The enthalpy and entropy changes depend on the length and nature of the loop region. For a peptide with three helical sections: protonated AcA14KG3A14KG3A14K; a coiled-coil bundle with three helices side-by-side is substantially less stable than a geometry with two helices in an antiparallel coiled-coil and the third helix collinear with one of the other two.
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Published online April 13, 2007
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Zilch, L.W., Kaleta, D.T., Kohtani, M. et al. Folding and unfolding of helix-turn-helix motifs in the gas phase. J Am Soc Mass Spectrom 18, 1239–1248 (2007). https://doi.org/10.1016/j.jasms.2007.03.027
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DOI: https://doi.org/10.1016/j.jasms.2007.03.027