Intrinsic motions may allow HIV-1 TAR RNA to change its conformation to form a functional complex with the Tat protein, which is essential for viral replication. Understanding the dynamic properties of TAR necessitates determining motion on the intermediate ns-μs time scale. To this end, we performed solid-state deuterium NMR line shape and T1Z relaxation time experiments to measure intermediate motions for two uridine residues, U40 and U42, within the lower helix of TAR. We infer global motions at rates of ~10(5) s(-1) in the lower helix, which are much slower than those of the upper helix (~10(6) s(-1)), indicating the two helical domains reorient independently of one another in the solid-state sample. These results contribute to the aim of fully describing the properties of functional motions in TAR RNA.
Ultraslow Domain Motions in HIV-1 TAR RNA Revealed by Solid-State Deuterium NMR.