Lighting up Nobel Prize-winning studies with protein intrinsic disorder.

Intrinsically disordered proteins and regions (IDPs and IDRs) and their importance in biology are becoming increasingly recognized in biology, biochemistry, molecular biology and chemistry textbooks, as well as in current protein science and structural biology curricula. We argue that the sequence → dynamic conformational ensemble → function principle is of equal importance as the classical sequence → structure → function paradigm. To highlight this point, we describe the IDPs and/or IDRs behind the discoveries associated with 17 Nobel Prizes, 11 in Physiology or Medicine and 6 in Chemistry. The Nobel Laureates themselves did not always mention that the proteins underlying the phenomena investigated in their award-winning studies are in fact IDPs or contain IDRs. In several cases, IDP- or IDR-based molecular functions have been elucidated, while in other instances, it is recognized that the respective protein(s) contain IDRs, but the specific IDR-based molecular functions have yet to be determined. To highlight the importance of IDPs and IDRs as general principle in biology, we present here illustrative examples of IDPs/IDRs in Nobel Prize-winning mechanisms and processes.

The pro-sequence of parathyroid hormone prevents premature amyloid fibril formation.

The parathyroid hormone (PTH) regulates the calcium and phosphate level in blood after secretion from parathyroid chief cells. The pre- and pro-sequences of precursor preproPTH get cleaved during PTH maturation. In secretory granules, PTH forms functional amyloids. Using thioflavin T fibrillation assays, circular dichroism, NMR spectroscopy, and cellular cAMP activation, we show that the pro-sequence prevents premature fibrillation by impairing primary nucleation because of Coulomb repulsion of positively charged residues. Under seeding or high salt conditions or in the presence of heparin at pH 5.5, proPTH fibril formation is delayed, but the monomer release properties are conserved. ProPTH can still activate in cellulo PTH receptor 1 but with impaired potency. These findings give some perspectives on medical applications of PTH in hormone therapy.

α-Synuclein Dimers as Potent Inhibitors of Fibrillization.

Aggregation of the neuronal protein α-synuclein into amyloid fibrils plays a central role in the development of Parkinson's disease. Growth of fibrils can be suppressed by blocking fibril ends from their interaction with monomeric proteins. In this work, we constructed inhibitors that bind to the ends of α-synuclein amyloid fibrils with very high affinity. They are based on synthetic α-synuclein dimers and interact with fibrils via two monomeric subunits adopting conformation that efficiently blocks fibril elongation. By tuning the charge of dimers, we further enhanced the binding affinity and prepared a construct that inhibits fibril elongation at nanomolar concentration (IC50 ≈ 20 nM). To the best of our knowledge, it is the most efficient inhibitor of α-synuclein fibrillization.