Hidden Structure in Disordered Proteins is Adaptive to Intracellular Changes

Abstract

Intrinsically disordered protein regions (IDRs) are ubiquitous in all proteomes and essential to cellular function. Unlike folded domains, IDRs exist in an ensemble of rapidly changing conformations. The sequence-encoded structural biases in IDR ensembles are important for function, but are difficult to resolve. Here, we reveal hidden structural preferences in IDR ensembles in vitro with two orthogonal structural methods (SAXS and FRET), and demonstrate that these structural preferences persist in cells using live cell microscopy. Importantly, we demonstrate that some IDRs have structural preferences that can adaptively respond to even mild intracellular environment changes, while other IDRs may display a remarkable structural resilience. We propose that the ability to sense and respond to changes in cellular physicochemical composition, or to resist such changes, is a sequence-dependent property of IDRs in organisms across all kingdoms of life.

Keywords: disordered proteins, live-cell imaging, FRET, SAXS, solution conditions, cellular environment Introduction