Introducing intrinsic disorder reduces electrostatic steering in protein-protein interactions

Area of Science:

• Biochemistry
• Structural Biology
• Computational Biology

Background:

• Protein-protein interactions are vital for cellular functions, with electrostatics influencing complex stability and specificity.
• Intrinsically disordered proteins (IDPs) represent a significant portion of the proteome, and their binding properties are extensively studied.
• The impact of structural disorder on electrostatic steering in protein binding remains largely unexplored.

Purpose of the Study:

• To investigate how intrinsic structural disorder affects electrostatic steering in protein-protein interactions.
• To analyze the consequence of disorder on the binding kinetics and thermodynamics of the E3/Im3 complex.

Main Methods:

• Utilized molecular dynamics simulations to model the E3/Im3 complex in both ordered and disordered states.
• Performed mechanistic analysis to compare binding mechanisms and interaction energetics between the two states.
• Examined the response of complex stability and kinetics to varying salt concentrations.

Main Results:

• The study recapitulated experimental findings showing reduced sensitivity to salt concentration for the disordered E3/Im3 complex compared to the ordered form.
• Mechanistic analysis indicated that the core native contact interactions in the encounter and transition states were similar for both ordered and disordered E3.
• The observed differences in electrostatic steering were attributed to conformational variations rather than alterations in the binding mechanism.

Conclusions:

• The findings suggest that conformational differences, not changes in the binding mechanism, underlie the altered electrostatic steering in disordered proteins.
• Increasing structural disorder is predicted to generally modulate the influence of electrostatic steering in protein-protein interactions.
• This has implications for understanding the role of IDPs in biological processes and drug design.