Intrinsically disordered proteins: lessons from colicins

Defining structural features of IDPs (intrinsically disordered proteins) and relating these to biological function requires characterization of their dynamical properties. In the present paper, we review what is known about the IDPs of colicins, protein antibiotics that use their IDPs to enter bacterial cells. The structurally characterized colicin IDPs we consider contain linear binding epitopes for proteins within their target cells that the colicin hijacks during entry. We show that these binding epitopes take part in intramolecular interactions in the absence of protein partners, i.e. self-recognition, and consider the structural origins of this and its functional implications. We suggest that self-recognition is common in other IDPs that contain similar types of binding epitopes.