Conformational analysis of an intrinsically disordered RNA binding domain

GAUTO DF; SUAREZ IP; HAILS G; RASIA RM

Sierra de la Ventana

Congreso; XLIII Reunión Anual de la Sociedad Argentina de Biofísica; 2014

Sociedad Argentina de Biofísica

A large fraction of the eukaryotic proteome is composed of Intrinsically disordered proteins (IDPs) and intrinsically disordered regions within larger proteins. For a subset of IDPs their function is linked to the acquisition of a folded structure upon partner recognition. An unresolved issue in this subset of IDPs is whether the sampling of conformational space is in a way linked to their ability to recognize different partners. In the present work we investigate the exploration of the conformational space by the first dsRBD of DCL1 from A. thaliana. This domain acquires a folded conformation with a complex topology upon binding dsRNA. We make use of NMR observables to identify the sampling at residue level. The protein shows a narrow distribution of chemical shifts, indicating its disordered nature. However titration with urea leads to further narrowing, showing that the native state is not fully unfolded. We find that different regions of the protein show a varying degree of unfolding with urea, suggesting that partial structuring is not homogeneous along the protein. Finally with the help of secondary chemical shifts and residual dipolar couplings we achieve a physical description of the disordered state in terms of a ensemble of structures.