Dynamicin vivomapping of the methylproteome using a chemoenzymatic approach

Abstract

Dynamic protein post-translation methylation is essential for cellular function, highlighted by the essential role of methylation in transcriptional regulation and its aberrant dysregulation in diseases including cancer. This underscores the importance of cataloging the cellular methylproteome. However, comprehensive analysis of the methylproteome remains elusive due to limitations in current enrichment and analysis pipelines. Here, we employ an L-Methionine analogue, ProSeMet, that is chemoenzymatically converted to the SAM analogue ProSeAM in cells and mice to tag proteins with a biorthogonal alkyne that can be functionalized for global detection, selective enrichment, and LC-MS/MS identification. We identify 486 proteins known to be methylated and 221 proteins with novel methylation sites encompassing diverse cellular functions. Systemic ProSeMet delivery in mice pseudomethylates proteins across organ systems with blood-brain barrier penetrance. Leveraging this pipeline to define the cellular methylproteome may have broad applications for understanding the methylproteome in the context of disease.