There are proteins known as "Intrinsically Unstructured Proteins" or "disordered" proteins. That function with no fixed configuration. Typically a good way of thinking about them is an ensemble of transient more common states, where things like post translational modification alters how long and which conformations the protein visits. The other replies you've gotten are inaccurate and about 15+ years out of date in thinking about protein structure.

Think of a roiling noodle where sections or the whole thing linger in certain shapes and configurations longer than in other positions.

This paper can give you a better idea about MYC specifically https://europepmc.org/article/MED/22457068

If you want to know more about disordered proteins in human DisProt is a good place to start https://disprot.org