Slice Collision-Induced Unfolding and Molecular Dynamics Reveal How Post-Translational Succination Reshapes SUMO1 Unfolding Pathways

SUMO1 (small ubiquitin-like modifier 1) is a central feature of post-translational SUMOylation, modifying a broad range of substrate proteins. SUMO1 itself is prone to succination, i.e., a post-translational Michael addition of cysteine onto fumarate, which results in the formation of succinated SUMO1 with modified properties. The present study assesses the structural and gas-phase stability modifications in SUMO1 induced by diethyl fumarate succination using advanced ion mobility spectrometry-mass spectrometry (IMS-MS) techniques. Among them, collision-induced unfolding (CIU) and slice-CIU highlight a modified unfolding process resulting from the creation of specific charge-dipole interactions involving the appended dicarbonyl moiety. The experimental results are further supported by molecular dynamics simulations to understand, at the atomistic level, the mechanisms underlying the CIU of gaseous (derivatized) SUMO1 ions.