Characterization of conformational dynamics at microsecond timescale in the RNA-binding regions of dsRNA-binding domains

Double-stranded RNA-binding domains (dsRBDs) are involved in a variety of biological functions via recognition and processing of dsRNAs. Though the primary substrate of the dsRBDs are dsRNAs with A-form helical geometry; they are known to interact with structurally diverse dsRNAs. Here, we have employed two model dsRBDs, TAR-RNA binding protein and Adenosine deaminase that acts on RNA, to understand the role of intrinsic protein dynamics in RNA binding. We have performed a detailed characterization of the residue-level dynamics by NMR spectroscopy for the two dsRBDs. While the dynamics profiles at the ps-ns timescale of the two dsRBDs were found to be different, a striking similarity was observed in the μs-ms timescale dynamics for both the dsRBDs. Motions at fast μs timescale (kex > 50000 s-1) were found to be present not only in the RNA-binding residues but also in some allosteric residues of the dsRBDs. We propose that this intrinsic μs timescale dynamics in two distinct dsRBDs allows them to undergo conformational rearrangement that may aid dsRBDs to target substrate dsRNA from the pool of structurally different RNAs in cellular environment.