1.3.4 Coil conformations
In addition to the repetitive helical and pleated sheet structures, there are other non-repetitive, and therefore more varied, elements of secondary structure called coil conformations. The lack of regular repetitive order in coil conformations does not, however, mean that these structures are disordered or unstable. In fact, it is clear from X-ray diffraction studies of proteins that these regions are consistent in the conformation that they adopt.
Regions of disorder do exist, however, in some proteins. Sometimes referred to as random coil, such regions may play an important part in the protein's function. For instance, random coil may be involved in the binding of a ligand, with consequent changes in the conformation and activity of the protein.