Thermodynamic consequences of Tyr to Trp mutations in the cation-π-mediated binding of trimethyllysine by the HP1 chromodomain

Mackenzie W Krone; Katherine I Albanese; Gage O Leighton; Cyndi Qixin He; Ga Young Lee; Marc Garcia-Borràs; Alex J Guseman; David C Williams Jr; K N Houk; Eric M Brustad; Marcey L Waters

doi:10.1039/d0sc00227e

Thermodynamic consequences of Tyr to Trp mutations in the cation-π-mediated binding of trimethyllysine by the HP1 chromodomain

Chem Sci. 2020 Mar 4;11(13):3495-3500. doi: 10.1039/d0sc00227e.

Affiliations

¹ University of North Carolina at Chapel Hill 131 South Road, Campus Box 3290 Chapel Hill NC 27599 USA mlwaters@email.unc.edu.
² Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill 120 Mason Farm Rd, Campus Box 7260 Chapel Hill NC 27599 USA.
³ Department of Chemistry and Biochemistry, University of California at Los Angeles 607 Charles E. Young Drive East, Box 951569 Los Angeles CA 90095-1569 USA.
⁴ Department of Pathology and Laboratory Medicine, University of North Carolina at Chapel Hill Campus Box 7525, Brinkhous-Bullitt Building Chapel Hill NC 27599 USA.
⁵ Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill 450 West Drive Chapel Hill NC 27599 USA.

Abstract

Evolution has converged on cation-π interactions for recognition of quaternary alkyl ammonium groups such as trimethyllysine (Kme3). While computational modelling indicates that Trp provides the strongest cation-π interaction of the native aromatic amino acids, there is limited corroborative data from measurements within proteins. Herein we investigate a Tyr to Trp mutation in the binding pocket of the HP1 chromodomain, a reader protein that recognizes Kme3. Binding studies demonstrate that the Trp-mediated cation-π interaction is about -5 kcal mol^-1 stronger, and the Y24W crystal structure shows that the mutation is not perturbing. Quantum mechanical calculations indicate that greater enthalpic binding is predominantly due to increased cation-π interactions. NMR studies indicate that differences in the unbound state of the Y24W mutation lead to enthalpy-entropy compensation. These results provide direct experimental quantification of Trp versus Tyr in a cation-π interaction and afford insight into the conservation of aromatic cage residues in Kme3 reader domains.

Thermodynamic consequences of Tyr to Trp mutations in the cation-π-mediated binding of trimethyllysine by the HP1 chromodomain

Authors

Affiliations

Abstract

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