A Bioorthogonal Chemical Reporter for the Detection and Identification of Protein Lactylation

L-Lactylation is a recently discovered post-translational modification occurring on histone lysine residues to regulate gene expression. However, the substrate scope of lactylation, especially that in non-histone proteins, remains unknown, largely due to the limitations of current methods for analyzing lactylated proteins. Herein, we report an alkynyl-functionalized bioorthogonal chemical reporter, YnLac, for the detection and identification of protein lactylation in mammalian cells. Our in-gel fluorescence and chemical proteomic analyses show that YnLac is metabolically incorporated into lactylated proteins and directly labels known lactylated lysines of histones. We further apply YnLac to the proteome-wide profiling of lactylation, revealing many novel modification sites in non-histone proteins for the first time.