On the Impact of Post-Translational Succination on SUMO1 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 (PTM) of critical cardiomyocyte proteins, including SERCA2a, a calcium pump essential for Ca2+ reuptake during heart muscle relaxation1. SUMOylation plays a pivotal role in regulating various cellular processes, such as protein localization, functional modulation, and complex formation2. Notably, SUMO1 contains a cysteine residue in its sequence, making it susceptible to succination, i.e. a Michael addition of cysteine to fumarate3 (Figure 1). This could occur in conditions of elevated intracellular fumarate concentration, a hallmark of metabolic dysregulation potentially associated with cardiotoxicity. To investigate this hypothesis, we employ a multidisciplinary approach, integrating advanced analytical techniques such as mass spectrometry (including 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 and its potential role in cardiac dysfunction.