Kovinko, A. | Search bioRxiv

bioRxiv2026

Emergence of new function through evolutionary divergence of an intrinsically disordered region

Intrinsically disordered regions (IDRs) are major drivers of protein functional diversification, yet the molecular features that enable the emergence of new functions within disordered sequences remain poorly understood. FCHO1 and FCHO2 are paralogous pioneer proteins of clathrin-mediated endocytosis that share a conserved domain architecture but perform distinct cellular functions and cannot compensate for each other's loss. Here we show that functional divergence between these proteins is associated with the acquisition of transient structure within their disordered regions. Using nuclear magnetic resonance spectroscopy, we identify two highly populated -helical elements in the IDR of FCHO1 that are absent from FCHO2. One of these helices mediates FCHO1 self-association and drives intracellular assembly, whereas FCHO2 lacks this behavior. Introduction of the FCHO1 helix into FCHO2 is sufficient to confer self-association and cellular assembly, demonstrating that a transient structural element embedded within an IDR can act as a transferable functional module. Evolutionary analysis reveals that this helical propensity emerged following duplication of the ancestral FCHO gene and became progressively reinforced during evolution. Despite this divergence, the same region retains a conserved membrane-binding activity in both paralogs. Together, our findings show how acquisition of transient secondary structure within an intrinsically disordered region can generate new molecular behaviors while preserving ancestral functions, providing a mechanism for the functional specialization of paralogous proteins.

biophysics↗

bioRxiv2026

Atomic structure and dynamics of the mechanosensitive channel MscL from E. coli by cryo-EM and solid-state NMR

Mechanosensitive channels are central to cellular responses to membrane tension, yet the structural basis of their gating remains incompletely understood. Here, we determine the structures of wild-type and G22S mutants of MscL from E. coli (EcMscL) by cryo-EM in peptide-based lipid nanodiscs and complement them with solid-state NMR measurements in liposomes to capture their dynamics in a native-like membrane environment. The cryo-EM structures reveal a closed conformation, whereas analysis of the low-threshold G22S mutant by NMR uncovers widespread conformational changes in both cytoplasmic and periplasmic regions. These data indicate enhanced dynamics and conformational heterogeneity in the mutant, revealing the early transitions from the closed towards the open state. Together, our results establish a synergistic framework integrating cryo-EM and NMR to resolve both structure and dynamics of mechanosensitive channels, and identify lipid-protein interactions as key determinants of MscL gating and mechanosensitivity. Our study further provides a quantitative benchmark for computational investigations of mechanogating and lays the foundation for the rational design of channels with tunable gating kinetics. TeaserBy integrating cryo-EM and solid-state NMR, we reveal how lipid-coupled dynamics prime MscL for opening, capturing the earliest transitions from closed to active states.

biophysics↗