Characterizing the Conformational Dynamics of Human SUMO2: Insights into its Interaction with Metal Ions and SIMs.

SUMO (Small Ubiquitin-like Modifiers) proteins are involved in a crucial post-translational modification commonly termed as SUMOylation. In this work, we have investigated the native-state conformational flexibility of human SUMO2 and its interaction with Cu2+ and Zn2+ ions using 15N/1H based 2D NMR spectroscopy. After SUMO1, SUMO2 is the most studied SUMO isoform in humans which shares 45% and ~80% similarity with SUMO1 in terms of sequence and structure, respectively. We show that compared to SUMO1, several amino acids in SUMO2 around α1-helix region access energetically similar near-native conformations. This could play a crucial role in its non-covalent interactions with SUMO interaction motifs (SIMs). A strong binding with Cu2+ ions in the C-terminal and resulting aggregation into timers as shown by gel-electrophoresis studies seem to interefere in it's non-covalent interaction with a V/I-x-V/I-V/I based SIM in Daxx protein.