TY - JOUR TI - Conformational and oligomeric states of SPOP from small-angle X-ray scattering and molecular dynamics simulations AU - Thomasen, F Emil AU - Cuneo, Matthew J AU - Mittag, Tanja AU - Lindorff-Larsen, Kresten A2 - Cui, Qiang A2 - Dötsch, Volker A2 - Yang, Sichun VL - 12 PY - 2023 DA - 2023/03/01 SP - e84147 C1 - eLife 2023;12:e84147 DO - 10.7554/eLife.84147 UR - https://doi.org/10.7554/eLife.84147 AB - Speckle-type POZ protein (SPOP) is a substrate adaptor in the ubiquitin proteasome system, and plays important roles in cell-cycle control, development, and cancer pathogenesis. SPOP forms linear higher-order oligomers following an isodesmic self-association model. Oligomerization is essential for SPOP’s multivalent interactions with substrates, which facilitate phase separation and localization to biomolecular condensates. Structural characterization of SPOP in its oligomeric state and in solution is, however, challenging due to the inherent conformational and compositional heterogeneity of the oligomeric species. Here, we develop an approach to simultaneously and self-consistently characterize the conformational ensemble and the distribution of oligomeric states of SPOP by combining small-angle X-ray scattering (SAXS) and molecular dynamics (MD) simulations. We build initial conformational ensembles of SPOP oligomers using coarse-grained molecular dynamics simulations, and use a Bayesian/maximum entropy approach to refine the ensembles, along with the distribution of oligomeric states, against a concentration series of SAXS experiments. Our results suggest that SPOP oligomers behave as rigid, helical structures in solution, and that a flexible linker region allows SPOP’s substrate-binding domains to extend away from the core of the oligomers. Additionally, our results are in good agreement with previous characterization of the isodesmic self-association of SPOP. In the future, the approach presented here can be extended to other systems to simultaneously characterize structural heterogeneity and self-assembly. KW - self-assembly KW - small-angle x-ray scattering KW - protein structure KW - isodesmic KW - molecular simulations JF - eLife SN - 2050-084X PB - eLife Sciences Publications, Ltd ER -