Proteome-Wide Analysis of Protein Lysine -Homocysteinylation in .

Protein -homocysteinylation by a homocysteine (Hcy) metabolite, Hcy-thiolactone, is an emerging post-translational modification (PTM) that occurs in all tested organisms and has been linked to human diseases. The yeast is widely used as a model eukaryotic organism in biomedical research, including studies of protein PTMs. However, patterns of global protein -homocysteinylation in yeast are not known. Here, we identified 68 and 197 -homocysteinylation sites at protein lysine residues (-Hcy-Lys). Some of the -homocysteinylation sites overlap with other previously identified PTM sites. Protein -homocysteinylation , induced by supplementation of yeast cultures with Hcy, which elevates Hcy-thiolactone levels, was accompanied by significant changes in the levels of 70 yeast proteins (38 up-regulated and 32 down-regulated) involved in the ribosomal structure, amino acid biosynthesis, and basic cellular pathways. Our study provides the first global survey of -homocysteinylation and accompanying changes in the yeast proteome caused by elevated Hcy level. These findings suggest that protein -homocysteinylation and dysregulation of cellular proteostasis may contribute to the toxicity of Hcy in yeast. Homologous proteins and -homocysteinylation sites are likely to be involved in Hcy-related pathophysiology in humans and experimental animals. Data are available via ProteomeXchange with identifier PXD020821.