# Computing the pH-Dependent Thermodynamics of the Allostery between Dimerization and Palmitate Binding in β‑Lactoglobulin

## TL;DR

This paper explores how pH affects the allostery of β-lactoglobulin, focusing on dimerization and palmitate binding.

## Contribution

The study introduces a pH-dependent thermodynamic linkage approach to analyze allostery in β-lactoglobulin.

## Key findings

- Dimerization is more favorable near the isoionic point.
- Palmitate binding is more favorable around pH 6–7.
- Ligand binding and dimerization have an antagonist relationship in pH 3–8.

## Abstract

The study of pH-dependent allosteric processes presents
a significant
challenge, both experimentally and computationally. In this work,
we apply the constant-pH molecular dynamics method to explore an interesting
case of allostery involving protein–ligand binding and dimerization.
As a model system, we use β-lactoglobulin (BLG), a small protein
from bovine milk known to dimerize and bind palmitic acid in a hydrophobic
pocketboth processes sensitive to pH. This study focuses on
the holo form of BLG, and, when combined with our previous study of
the apo form (da Rocha et al. J. Chem. Theory Comput.
2022 18, 1982), completes the thermodynamic cycle of
the allosteric process. The corresponding pH-dependent free energy
profiles are obtained through the use of a thermodynamic linkage relation,
avoiding the need of performing heavy computational calculations.
Dimerization is found to be more favorable near the isoionic point,
as observed in the apo form. Palmitate binding is found to be more
favorable around pH 6–7, a biologically relevant pH range at
which the gate covering the binding site is known to open. A pH-dependent
measure of allosteric coupling is computed, showing that ligand binding
and dimerization exhibit an antagonist relationship within the studied
pH range of 3–8, with binding destabilizing dimerization and
vice versa.