Thermodynamics of The Interactions of FG‐Nucleoporins and Transport Factors

Abstract

Intrinsically disordered proteins (IDPs) play important roles in many biological systems. Given the vast conformational space that IDPs can explore, the thermodynamics of the interactions with their partners is closely linked to their biological functions. Intrinsically disordered regions of Phe–Gly nucleoporins (FG Nups) that contain multiple phenylalanine–glycine repeats are of particular interest, as their interactions with transport factors (TFs) underlie the paradoxically rapid yet also highly selective transport of macromolecules mediated by the nuclear pore complex (NPC). Here, we used NMR and isothermal titration calorimetry (ITC) to thermodynamically characterize these multivalent interactions. These analyses revealed that a combination of low per-FG motif affinity and the enthalpy–entropy balance prevents high avidity interaction between FG Nups and TFs, while the large number of FG motifs promotes frequent FG–TF contacts, resulting in enhanced selectivity. Our thermodynamic model underlines the importance of functional disorder of FG Nups. It helps explain the rapid and selective translocation of TFs through the NPC and further expands our understanding of the mechanisms of “fuzzy” interactions involving IDPs. Support or Funding Information Funded by Grants R01 GM112108, P41 GM109824, U01 GM098256 (to MPR), R01 GM117212 and S10 OD016305 (to DC), and P30 CA013330. Thermodynamics of FSFGNTF2 interaction. (A) Gibbs free energy (ΔG) for the interactions between FSFG constructs and NTF2. (B) Gibbs free energy (ΔG), enthalpy (ΔH) and entropy (− TΔS) for the interactions between FSFG4-FSFG12 constructs and NTF2 measured by ITC. (C) Enthalpy entropy compensation curve for interactions for the aforementioned constructs, with a linear fit (D) Schematic diagram of the enthalpy-entropy balance that prevents high avidityinteractions. This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.