Analysis of Multivalent IDP Interactions: Stoichiometry, Affinity, and Local Concentration Effect Measurements

Area of Science:

• Biochemistry
• Biophysics
• Molecular Biology

Background:

• Intrinsically disordered proteins (IDPs) play crucial roles in cellular processes.
• The nuclear pore complex (NPC) mediates selective transport via interactions between FG-nucleoporins (FG-Nups) and nuclear transport factors (NTRs).
• Understanding the thermodynamic basis of these multivalent interactions is key to explaining transport selectivity.

Purpose of the Study:

• To detail methods for assessing enthalpy-entropy balance in multivalent IDP interactions.
• To apply these methods to FG-Nup/NTR interactions.
• To elucidate the mechanisms underlying selective macromolecular transport through the NPC.

Main Methods:

• Nuclear magnetic resonance (NMR) titration.
• Isothermal titration calorimetry (ITC).
• Dynamic light scattering (DLS) analysis.

Main Results:

• Combined NMR and ITC provide insights into enthalpy-entropy balance in multivalent IDP interactions.
• FG-Nup/NTR interactions exhibit low per-motif affinity.
• An enthalpy-entropy balance prevents high-avidity binding, while numerous FG motifs ensure frequent contacts, enhancing selectivity.

Conclusions:

• The study provides a detailed methodology for analyzing complex protein interactions.
• The findings elucidate the thermodynamic principles governing FG-Nup/NTR interactions.
• This work contributes to understanding the mechanism of selective transport through the NPC.