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 in vitro, leading to important conformational changes. These findings provide insights into the susceptibility of SUMO1 to metabolic alterations.