Lošdorfer Božič Anže, Podgornik Rudolf
Department of Theoretical Physics, Jožef Stefan Institute, Ljubljana, Slovenia.
Department of Theoretical Physics, Jožef Stefan Institute, Ljubljana, Slovenia; Department of Physics, Faculty of Mathematics and Physics, University of Ljubljana, Ljubljana, Slovenia.
Biophys J. 2017 Oct 3;113(7):1454-1465. doi: 10.1016/j.bpj.2017.08.017.
Electrostatic interactions play a fundamental role in the structure and function of proteins. Due to ionizable amino acid residues present on the solvent-exposed surfaces of proteins, the protein charge is not constant but varies with the changes in the environment-most notably, the pH of the surrounding solution. We study the effects of pH on the charge of four globular proteins by expanding their surface charge distributions in terms of multipoles. The detailed representation of the charges on the proteins is in this way replaced by the magnitudes and orientations of the multipole moments of varying order. Focusing on the three lowest-order multipoles-the total charge, dipole, and quadrupole moment-we show that the value of pH influences not only their magnitudes, but more notably and importantly also the spatial orientation of their principal axes. Our findings imply important consequences for the study of protein-protein interactions and the assembly of both proteinaceous shells and patchy colloids with dissociable charge groups.
静电相互作用在蛋白质的结构和功能中起着基础性作用。由于蛋白质溶剂暴露表面存在可电离的氨基酸残基，蛋白质电荷并非恒定不变，而是随环境变化而变化——最显著的是周围溶液的pH值。我们通过用多极展开蛋白质表面电荷分布来研究pH对四种球状蛋白质电荷的影响。这样，蛋白质上电荷的详细表示就被不同阶次多极矩的大小和方向所取代。聚焦于三个最低阶的多极——总电荷、偶极矩和四极矩——我们表明pH值不仅影响它们的大小，更显著且重要的是还影响其主轴的空间取向。我们的研究结果对蛋白质 - 蛋白质相互作用以及具有可解离电荷基团的蛋白质外壳和补丁胶体的组装研究具有重要意义。
