Mechanism of ribonucleoprotein low complexity domain molecule oligomerization: Experimental investigations and...

Nucleation of RNA-binding proteins is the first step in forming functional RNA-protein complexes (RNPs), which control various aspects of RNA metabolism. Nucleation of proteins involved in neurodegeneration can occur through an oligomerization process; however, the mechanism which causes this process remains unknown. Therefore, in this work, we focused on the study of the oligomeric structure of the heterogeneous nuclear ribonucleoprotein A2 low complexity domain (hnRNPA2 LCD) molecule, one of the important proteins involved in RNA metabolism. Various experimental and theoretical techniques were applied to determine essential physicochemical parameters of the protein in solutions of various ionic strengths and pHs. The protein monomer size, its cross-sectional area, and the dependence of nominal charge on pH, comprising the isoelectric point, were theoretically evaluated. This data allowed the determination of the adsorption kinetics of hnRNPA2 LCD molecules on mica and polymer microparticles using the streaming potential measurements and laser Doppler velocimetry, respectively. It was shown that the protein was adsorbed in the form of oligomers, the size distribution of which was determined by atomic force microscopy. Additionally, molecular dynamics modeling was applied to gain insight into the mechanism of pH-driven changes in protein molecule conformations and their influence on the oligomerization process. Besides its significance to basic science, the acquired results enabled the development of an effective method for quantifying the oligomerization kinetics of unstable protein solutions.