Abstract

Molecular communication in biology is mediated by protein interactions. According to the current paradigm, the specificity and affinity required for these interactions are encoded in the precise complementarity of binding interfaces. Even proteins that are disordered under physiological conditions or that contain large unstructured regions commonly interact with well-structured binding sites on other biomolecules. We recently discovered an unexpected interaction mechanism: The two intrinsically disordered human proteins histone H1 and its nuclear chaperone prothymosin α associate in a one-to-one complex with picomolar affinity, but they fully retain their structural disorder, long-range flexibility, and highly dynamic character. Based on the close integration of single-molecule experiments, NMR , and molecular simulations, we obtained a detailed picture of this complex that can be explained by the large opposite net charge of the two proteins without requiring defined binding sites or interactions between specific individual residues. This type of interaction has interesting ramifications for kinetic mechanisms of binding and cellular regulation.

Borgia, A., Borgia, M., Bugge, K., Kissling, V.M., Heidarsson, P.O., Fernandes, C.B., Sottini, A., Soranno, A., Buholzer, K., Nettels, D., Kragelund, B.B., Best, R.B., & Schuler, B. (2018) Extreme disorder in an ultra-high-affinity protein complex. Nature, 555, 61-66.