Controlling spontaneous protein self-assembly into microspheres in binary systems
Résumé
Controlling protein-protein interactions and assembly into reversible supramolecular structures of defined size and shape throughout the control of physicochemical conditions is an underdeveloped process, especially for binary systems, i.e. involving two proteins. One of the reasons comes from the complexity of such system and the lack of information on the key structural parameters governing protein assembly - protein size, molecular stability and flexibility, number of positive and negative charges and their repartition onto protein surface, etc.). Previously, we reported on the ability of lysozyme and alpha-lactalbumin, two globular proteins, to self-assemble into well-defined microspheres when placed in conditions where protein net charges are opposite in sign but of equal magnitude [1]. Formation of supramolecular structures followed by phase separation was also observed by mixing lysozyme and its succinylated form that carries opposite net charge [2]. In the present communication, we will address on the ability of oppositely charged globular proteins to interact and self-assemble into original spherical structures in different protein binary systems. We propose that self-assembly into microspheres is a universal form of molecular assembly as far as optimal physico-chemical conditions are adapted. In particular, the pH value for optimal formation of microspheres was found to be specific for each binary system [3]. Taking together, our results suggest that optimal protein assembly into microspheres in binary system is driven not only by “protein charge compensation” phenomenon but also by “protein size compensation”.