Biophysical Society Thematic Meeting| Lima 2019

Revisiting the Central Dogma of Molecular Biology at the Single-Molecule Level

Poster Abstracts

31-POS Board 31 EFFECT OF CHARGE REGULATION ON THE INTERACTION POTENTIALS OF PROTEINS Fredderico C. Machado ; Leandro R Barbosa 1 ; Francesco Spinozzi 2 ; 1 University of São Paulo, Department of General Physics, São Paulo, Brazil 2 Universita Politecnica delle Marche, Department of Life and Environmental Sciences, Ancona, Italy Protein Charge regulation is a subject that has been studied by various researchers groups around the world. The main idea of this methodology developed in the 50's is to consider a possible fluctuation in the value of the charges on the protein surface, generating a charge distribution not constant in this ensemble. This distribution may be affected by the presence of other macromolecules, such as proteins and polymers, or even due to changes in the medium, such as the addition of salts in the solution or pH variation. The aim of this study is to observe the effects of charge regulation from protein-protein interaction potentials using SAXS technique.We chose Random Phase Approximation (RPA) the closure relation to solve the Ornstein-Zernike equation. In this closing relation, the total potential of interaction between the proteins is divided in two contributions: Potential of reference, given by the potential of hard sphere; Potential of perturbation, given by Coulomb potential, Kirkwood potential (coming from the charge regulation theory) and attractive potential Yukawa type. Simulations were performed for Bovine Serum Albumin and Lysozyme and compared with experimental measurements. For the former, the term of charge regulation did not significantly influence the attractive potential (Yukawa type). For pHs 4 and 5, for example, despite the inclusion of the variance term of the charge, the value of potential at the contact, J, was not changed. As for lysozyme, in the pH's far from the isoelectric point (pI), the contact potential had its value diminished, thus showing that the regulation of charges may be an important factor for this protein. Due to these results, the hypothesis of charge regulation will be tested more clearly for proteins of smaller size, such as cytochrome C.

68