Nonenzymatic acetylation of ubiquitin Lys side chains is modulated by their neighboring residues.

Nonenzymatic acetylation of Lys side chains (Lys‐SCs) by various <italic>in vivo</italic> reactive molecules has been suggested to play novel regulatory roles. Ubiquitin (UB) has seven Lys residues that are utilized for synthesis of specific poly‐UB chains. To understand the nature of these Lys‐SC modifications, the chemical acetylation rate and p<italic>K</italic>_a and Hill coefficient of each UB‐Lys‐SC were measured. Mutagenesis studies combined with the determination of activation energy indicated that specific neighboring residues of the Lys‐SCs have a potential catalytic activity during nonenzymatic acetylation. Based on the shared chemistry between nonenzymatic Lys acetylation and ubiquitylation, the characterized chemical properties of the UB‐Lys‐SCs could be a reference for deciphering both mechanisms. Our NMR approaches could be useful for studying general nonenzymatic Lys acylations of various proteins. [ABSTRACT FROM AUTHOR]