Impact of Post-Translational Succination on Small Ubiquitin-Like Modifier 1 Structure: A Dual Approach Combining Gas Phase and Solution Studies

SUMO1 (small ubiquitin-like modifier 1) is a key protein involved in the post-translational modification of a wide range of substrate proteins. SUMOylation plays a pivotal role in regulating various cellular processes such as protein localization, functional modulation, and complex formation. Notably, SUMO1 contains a cysteine residue in its sequence, making it susceptible to succination, i.e., a Michael addition of cysteine onto fumarate, forming a succinated cysteine. This could occur under conditions of elevated intracellular fumarate concentration, a hallmark of metabolic dysregulation. To investigate this hypothesis, we employ a multidisciplinary approach integrating advanced analytical techniques such as mass spectrometry (including liquid chromatography, ion mobility spectrometry, and hydrogen-deuterium exchange experiments), circular dichroism spectroscopy, and molecular dynamics simulations. We demonstrate that SUMO1 undergoes succination <i>in vitro</i>, leading to important conformational changes. These findings provide insights into the susceptibility of SUMO1 to metabolic alterations.