Pre- and post-docking sampling of conformational changes using ClustENM and HADDOCK for protein-protein and protein-DNA systems.

Incorporating the dynamic nature of biomolecules in the modeling of their complexes is a challenge, especially when the extent and direction of the conformational changes taking place upon binding is unknown. Estimating whether the binding of a biomolecule to its partner(s) occurs in a conformational state accessible to its unbound form ("conformational selection") and/or the binding process induces conformational changes ("induced-fit") is another challenge. We propose here a method combining conformational sampling using ClustENM-an elastic network-based modeling procedure-with docking using HADDOCK, in a framework that incorporates conformational selection and induced-fit effects upon binding. The extent of the applied deformation is estimated from its energetical costs, inspired from mechanical tensile testing on materials. We applied our pre- and post-docking sampling of conformational changes to the flexible multidomain protein-protein docking benchmark and a subset of the protein-DNA docking benchmark. Our ClustENM-HADDOCK approach produced acceptable to medium quality models in 7/11 and 5/6 cases for the protein-protein and protein-DNA complexes, respectively. The conformational selection (sampling prior to docking) has the highest impact on the quality of the docked models for the protein-protein complexes. The induced-fit stage of the pipeline (post-sampling), however, improved the quality of the final models for the protein-DNA complexes. Compared to previously described strategies to handle conformational changes, ClustENM-HADDOCK performs better than two-body docking in protein-protein cases but worse than a flexible multidomain docking approach. However, it does show a better or similar performance compared to previous protein-DNA docking approaches, which makes it a suitable alternative.