Structural Analysis of poly-SUMO Chain Recognition by RNF4-SIMs Domain

The E3 ubiquitin-protein ligase RNF4 contains four tandem SUMO interacting motif (SIM) repeats for selective interaction with poly-SUMO modified proteins, which it targets for degradation. We employed a multifaceted approach to characterise structures of the RNF4-SIMs domain and tetra-SUMO2 chain to elucidate the interaction between them. In solution, the SIMs domain was intrinsically disordered and the linkers of the tetra-SUMO2 were highly flexible. Individual SIMs of RNF4-SIMs domains bind to SUMO2 in the groove between the β2 strand and the α1-helix parallel to the β2 strand. SIM2 and SIM3 bound to SUMO with a high affinity and together constituted the recognition module necessary for SUMO binding. SIM4 alone bound to SUMO with low affinity; however, its contribution to tetra-SUMO2 binding avidity is comparable to that of SIM3 when in the RNF4-SIMs domain. The SAXS data of the tetra-SUMO2/RNF4-SIMs domain complex indicate that it exists as an ordered structure. The HADDOCK model showed that the tandem RNF4-SIMs domain bound antiparallel to the tetra-SUMO2 chain orientation and wrapped around the SUMO protamers in a superhelical turn without imposing steric hindrance on either molecule.

Source: BJ Signal - May 20, 2014 Category: Biochemistry Authors: C C.-H. Kung, M T. Naik, S Wang, H Shih, C Chang, L Lin, C Chen, C Ma, C Chang, T Huang Tags: BJ Biomolecules Source Type: research