CRYSTAL-STRUCTURE AT 1.92 ANGSTROM RESOLUTION OF THE RNA-BINDING DOMAIN OF THE U1A SPLICEOSOMAL PROTEIN COMPLEXED WITH AN RNA HAIRPIN

The crystal structure of the RNA-binding domain of the small nuclear r ibonucleoprotein U1A bound to a 21-nucleotide RNA hairpin has been det ermined at 1.92 Angstrom resolution. The ten-nucleotide RNA loop binds to the surface of the beta-sheet as an open structure, and the AUUGCA C sequence of the loop interacts extensively with the conserved RNP1 a nd RNP2 motifs and the C-terminal extension of the RNP domain. These i nteractions include stacking of RNA bases with aromatic side chains of proteins and many direct and water-mediated hydrogen bonds. The struc ture reveals the stereochemical basis for sequence-specific RNA recogn ition by the RNP domain.