title: U1A RNA-binding domain at 1.8 A resolution.
abstract: The human U1A RNA-binding domain (RBD1) adopts one of the most common protein folds, the RNA-recognition motif, and is a paradigm for understanding RNA-protein interactions. A 2.8 A resolution structure of the unbound RBD1 has previously been determined [Nagai et al. (1990). Nature (London), 348, 515-520] and revealed a well defined alpha/beta core with disordered termini. Using a longer construct, a 1.8 A resolution structure of the unbound domain was determined that reveals an ordered C-terminal helix. The presence of this helix is consistent with a solution structure of the free domain [Avis et al. (1996). J. Mol. Biol. 257, 398-411]; however, in the solution structure the helix occludes the RNA-binding surface. In the present structure, the helix occupies a position similar to that seen in a 1.9 A resolution RNA-RBD1 complex structure [Oubridge et al. (1994). Nature (London), 372, 432-438]. The crystals in this study were grown from 2.2 M sodium malonate. It is possible that the high salt concentration helps to orient the C-terminal helix in the RNA-bound conformation by strengthening hydrophobic interactions between the buried face of the helix and the alpha/beta core of the protein. Alternatively, the malonate (several molecules of which are bound in the vicinity of the RNA-binding surface) may mimic RNA.
authors.affiliation: Fred Hutchinson Cancer Research Center, USA.
authors.forename: Peter B
authors.initials: PB
authors.lastname: Rupert
authors.forename: Hong
authors.initials: H
authors.lastname: Xiao
authors.forename: Adrian R
authors.initials: AR
authors.lastname: Ferré-D'Amaré
mesh_terms: D020816:Amino Acid Motifs; D003460:Crystallization; D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000201:enzymology; D006801:Humans; D008958:Models, Molecular; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012313:RNA / Q000737:chemistry; D016601:RNA-Binding Proteins; D011994:Recombinant Proteins / Q000737:chemistry; D017412:Ribonucleoprotein, U1 Small Nuclear / Q000737:chemistry*
chemical_list: D016601:RNA-Binding Proteins; D011994:Recombinant Proteins; D017412:Ribonucleoprotein, U1 Small Nuclear; C075339:U1A protein; D012313:RNA