More than π-π-π stacking: Contribution of Amide-π and CH-π interactions to Crotonyllysine Binding by the AF9 YEATS Domain.

Lysine crotonylation (Kcr) is a histone post-translational modification that is implicated in numerous epigenetic pathways and diseases. Recognition of Kcr by YEATS domains has been proposed to occur through intermolecular amide-pi and alkene-pi interactions, but little is known about the driving force of these key interactions. Herein, we probed the recognition of lysine crotonylation and acetylation by the AF9 YEATS domain through incorporation of noncanonical Phe analogs with distinct electrostatics at two positions. We found that amide-pi interactions between AF9 and acyllysines are electrostatically tunable, with electron-rich rings providing more favorable interactions. This differs from trends in amide-heteroarene interactions and provides insightful information for therapeutic design. Additionally, we report for the first time that CH-pi interactions at Phe28 contribute to AF9's recognition of acyllysines, illuminating differences among YEATS domains, as this residue is not conserved but has been shown to impart selectivity for specific post-translational modification.