Open AccesspH-Dependent Interactions of Apolipophorin-III with a Lipid Disk
Author(s) -
Yunhui Peng,
Rudolfs Kelle,
C. M. Little,
Ekaterina Michonova,
K. G. Kornev,
Emil Alexov
Publication year - 2020
Publication title -
journal of computational biophysics and chemistry
Language(s) - English
Resource type - Journals
eISSN - 2737-4173
pISSN - 2737-4165
DOI - 10.1142/s2737416520420041
Subject(s) - population , range (aeronautics) , crystallography , biophysics , chemistry , stereochemistry , biochemistry , biology , materials science , demography , sociology , composite material
Apolipophorin-III (ApoLp-III) is required for stabilization of molecular shuttles of lipid fuels in insects and is found to contribute to the insect immune reaction. Rearrangement of its five [Formula: see text]-helices enables ApoLp-III to reversibly associate with lipids. We investigate computationally the conformational changes of ApoLp-III and the pH-dependence of the binding free energy of ApoLp-III association with a lipid disk. A dominant binding mode along with several minor, low population, modes of the ApoLp-III binding to a lipid disk was identified. The pH-dependence of the binding energy for ApoLp-III with the lipid disk is predicted to be significant, with the pH-optimum at pH[Formula: see text]. The calculations suggest that there are no direct interactions between the lipid head groups and titratable residues of ApoLp-III. In the physiological pH range from 6.0 to 9.0, the binding free energy of ApoLp-III with the lipid disk decreases significantly with respect to its optimal value at pH 8.0 (at pH[Formula: see text], it is 1.02[Formula: see text]kcal/mol and at pH[Formula: see text] it is 0.23[Formula: see text]kcal/mol less favorable than at the optimal pH[Formula: see text]), indicating that the pH is an important regulator of ApoLp-III lipid disk association.