Pressure, Motion, and Conformational Entropy in Molecular Recognition by Proteins

Authors

José A Caro
Kathleen G Valentine
Taylor R Cole
A Joshua Wand

Language

English

Publication Date

3-8-2023

Journal

Biophysical Reports

DOI

10.1016/j.bpr.2022.100098

PMID

36647534

PMCID

PMC9840116

PubMedCentral® Posted Date

12-28-2022

PubMedCentral® Full Text Version

Post-print

Abstract

The thermodynamics of molecular recognition by proteins is a central determinant of complex biochemistry. For over a half-century, detailed cryogenic structures have provided deep insight into the energetic contributions to ligand binding by proteins. More recently, a dynamical proxy based on NMR-relaxation methods has revealed an unexpected richness in the contributions of conformational entropy to the thermodynamics of ligand binding. Here, we report the pressure dependence of fast internal motion within the ribonuclease barnase and its complex with the protein barstar. In what we believe is a first example, we find that protein dynamics are conserved along the pressure-binding thermodynamic cycle. The femtomolar affinity of the barnase-barstar complex exists despite a penalty by −TΔSconf of +11.7 kJ/mol at ambient pressure. At high pressure, however, the overall change in side-chain dynamics is zero, and binding occurs with no conformational entropy penalty, suggesting an important role of conformational dynamics in the adaptation of protein function to extreme environments. Distinctive clustering of the pressure sensitivity is observed in response to both pressure and binding, indicating the presence of conformational heterogeneity involving less efficiently packed alternative conformation(s). The structural segregation of dynamics observed in barnase is striking and shows how changes in both the magnitude and the sign of regional contributions of conformational entropy to the thermodynamics of protein function are possible.

Published Open-Access

yes

Recommended Citation

Caro, José A; Valentine, Kathleen G; Cole, Taylor R; et al., "Pressure, Motion, and Conformational Entropy in Molecular Recognition by Proteins" (2023). Faculty and Staff Publications. 20.
https://digitalcommons.library.tmc.edu/ethics_pub/20