Phosphorylation of Histone Deacetylase 8: Structural and Mechanistic Analysis of Phosphomimetic S39E Mutant

Histone deacetylase (HDAC) enzymes that catalyze removal of acetyl-lysine post translational modifications are frequently post-translationally modified. HDAC8 is phosphorylated within the deacetylase domain at conserved residue serine 39 which leads to decreased catalytic activity. HDAC8 phosphorylation at S39 is unique in its location and function and may represent a novel mode of deacetylation regulation. To better understand the impact of phosphorylation of HDAC8 on enzyme structure and function, we performed crystallographic, kinetic, and molecular dynamics studies of the S39E HDAC8 phosphomimetic mutant. This mutation decreases deacetylation of peptides derived from acetylated nuclear and cytoplasmic proteins. However, the magnitude of the effect depends on the peptide sequence and the identity of the active site metal ion (Zn(II) vs Fe(II)) with the value of kcat/KM for the mutant decreasing 9- to >200-fold compared to wild-type HDAC8. Furthermore, the dissociation rate constant of the active site m...