Conformational flexibility in SUMO-1 protein (PDB:1a5r). The central part shows relatively ordered structure. Conversely, the N- and C-terminal regions (left and right, respectively) show ‘intrinsic disorder’, although a short helical region persists in the N-terminal tail. Ten alternative NMR models were morphed. Secondary structure elements: α-helices (red), β-strands (blue arrows). [1]
IDPs are a very large and functionally important class of proteins and their discovery has disproved the idea that three-dimensional structures of proteins must be fixed to accomplish their biological functions. For example, IDPs have been identified to participate in weak multivalent interactions that are highly cooperative and dynamic, lending them importance in DNA regulation and in cell signaling.[6][7] Many IDPs can also adopt a fixed three-dimensional structure after binding to other macromolecules. Overall, IDPs are different from structured proteins in many ways and tend to have distinctive function, structure, sequence, interactions, evolution and regulation.[8]