title: Structural basis for SUMO-E2 interaction revealed by a complex model using docking approach in combination with NMR data.
abstract: The interaction between small ubiquitin-related modifier SUMO and its conjugating-enzyme Ubc9 (E2) is an essential step in SUMO conjugation cascade. However, an experimental structure of such a transient complex is still unavailable. Here, a structural model of SUMO-3-Ubc9 complex was obtained with HADDOCK, combining NMR chemical shift mapping information. Docking calculations were performed using SUMO-3 and Ubc9 structures as input. The resulting complex reveals that the complementary surface electrostatic potentials contribute dominantly to the specific interaction. At the interface, similar numbers of oppositely-charged conserved residues are identified on the respective binding partners. Hydrogen bonds are formed in the vicinity of the interface to stabilize the complex. Comparison of the structure of SUMO-3-Ubc9 complex generated by HADDOCK and the experimental structures in free form indicates that SUMO-3 and Ubc9 maintain their respective fold as a whole after docking. However, the N-terminal helix alpha1 and its subsequent L1 loop of Ubc9 experience sizeable changes upon complex formation. They cooperatively move towards the hydrophilic side of the beta-sheet of SUMO-3. Our observations are consistent with the data from previous Ubc9 mutational analysis and conformational flexibility studies. Together, we have proposed that the SUMO-3-Ubc9 interaction is strongly electrostatically driven and the N terminus of Ubc9 shifts to SUMO-3 to facilitate the interaction. The NMR-based structural model, which provides considerable insights into the molecular basis of the specific SUMO-E2 recognition and interaction, implicates the general interaction mode between SUMO-3 and Ubc9 homologues from yeast to humans.
authors.affiliation: Hefei National Laboratory for Physical Sciences at Microscale, School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China.
authors.forename: Husheng
authors.initials: H
authors.lastname: Ding
authors.forename: Yuedong
authors.initials: Y
authors.lastname: Yang
authors.forename: Jiahai
authors.initials: J
authors.lastname: Zhang
authors.forename: Jihui
authors.initials: J
authors.lastname: Wu
authors.forename: Haiyan
authors.initials: H
authors.lastname: Liu
authors.forename: Yunyu
authors.initials: Y
authors.lastname: Shi
mesh_terms: D001665:Binding Sites; D002151:Calorimetry; D007700:Kinetics; D008958:Models, Molecular; D017433:Protein Structure, Secondary; D025841:Small Ubiquitin-Related Modifier Proteins / Q000737:chemistry* / Q000378:metabolism*; D055672:Static Electricity; D013816:Thermodynamics; D044763:Ubiquitin-Conjugating Enzymes / Q000737:chemistry* / Q000378:metabolism*; D000098843:Ubiquitin-Conjugating Enzyme UBC9
chemical_list: C117909:SUMO2 protein, human; D025841:Small Ubiquitin-Related Modifier Proteins; D044763:Ubiquitin-Conjugating Enzymes; D000098843:Ubiquitin-Conjugating Enzyme UBC9