IUP (protein)

IUP is the abbreviation for intrinsically unstructured protein. It exhibits an intrinsic propensity for being unstructured. IUPs are more prominent in eucaryotic species than procaryotic ones. This correlation suggests a crucial function in multicellular organization and complex signalling which are cancer-critical. Interestingly, intrinsically unstructured regions can be highly conserved and fold upon binding of target structures. Several databases of IUPs are launched which reflect the growing interest of the community in this formerly overlooked "new world" of protein structures.

Philosophically speaking, it is not really likely that there are any "unstructured" proteins. Even random coil ensembles have specific signatures which mediate specific functions and may rationalize high evolutionary conservation. This "hidden structure" may, however be frequently overlooked by standard techniques of nowadays structural biology.