1anr: Difference between revisions

Efficient transcription from the human immunodeficiency virus (HIV), promoter depends on binding of the viral regulatory protein Tat to a, cis-acting RNA regulatory element, TAR. Tat binds at a trinucleotide bulge, located near the apex of the TAR stem-loop structure. An essential feature, of Tat-TAR interaction is that the protein induces a conformational change, in TAR that repositions the functional groups on the bases and the, phosphate backbone that are critical for specific intermolecular, recognition of TAR RNA. We have previously determined a high resolution, structure for the bound form of TAR RNA using heteronuclear NMR. Here, we, describe a high resolution structure of the free TAR RNA based on 871, experimentally determined restraints. In the free TAR RNA, bulged residues, U23 and C24 are stacked within the helix, while U25 is looped out. This, creates a major distortion of the phosphate backbone between C24 and G26., In contrast, in the bound TAR RNA, each of the three residues from the, bulge are looped out of the helix and U23 is drawn into proximity with G26, through contacts with an arginine residue that is inserted between the two, bases. Thus, TAR RNA undergoes a transition from a structure with an open, and accessible major groove to a much more tightly packed structure that, is folded around basic side chains emanating from the Tat protein.

1ANR is a [http://en.wikipedia.org/wiki/Protein_complex Protein complex] structure of sequences from [http://en.wikipedia.org/wiki/ ]. Structure known Active Site: TAR. Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=1ANR OCA].  

''Page seeded by [http://ispc.weizmann.ac.il/oca OCA ] on Mon Nov  5 12:53:31 2007''