Linking post-translational modifications and protein turnover by site-resolved protein turnover (SPOT) profiling

Proteome-wide measurements of protein turnover have largely ignored the impact of post-translational modifications (PTMs). To address this gap, we employ stable isotope labelling and mass spectrometry to measure the turnover of >120,000 peptidoforms including >33,000 phosphorylated, acetylated and ubiquitinated peptides for >9,000 native proteins. This site-resolved protein turnover (SPOT) profiling discloses global and site-specific differences in turnover associated with the presence or absence of PTMs. While causal relationships may not always be immediately apparent, we hypothesize that PTMs with diverging turnover may distinguish states of differential protein stability, structure, localization, enzymatic activity, or protein-protein interactions. We exemplify how the turnover data may facilitate insights into unknown functions of PTMs and provide a web-tool for the scientific community that allows interrogation and visualisation of all turnover data. Since the methodology is applicable to many cell types and modifications, it has substantial potential to prioritize PTMs for functional investigation in the future.