So the simple possibility is rigid docking to get a surface between proteins. As with everything in biology, things can be more complicated. For example, from

So the simple possibility is rigid docking to get a surface between proteins. As with everything in biology, things can be more complicated. For example, from here : https://elifesciences.org/articles/22889 https://elifesciences.org/articles/22889 it starts with: >Many eukaryotic regulatory proteins adopt distinct bound and unbound conformations, and use this structural flexibility to bind specifically to multiple partners In other words, binding of a protein to another can change its shape (conformation).