Abstract of the PDB Structure's related Publication:
We have determined and refined a crystal structure of the initial assembly complex of archaeal box C/D sRNPs comprising the Archaeoglobus fulgidus (AF) L7Ae protein and a box C/D RNA. The box C/D RNA forms a classical kink-turn (K-turn) structure and the resulting protein-RNA complex serves as a distinct platform for recruitment of the fibrillarin-Nop5p complex. The cocrystal structure confirms previously proposed secondary structure of the box C/D RNA that includes a protruded U, a UU mismatch, and two sheared tandem GA base pairs. Detailed structural comparisons of the AF L7Ae-box C/D RNA complex with previously determined crystal structures of L7Ae homologs in complex with functionally distinct K-turn RNAs revealed a set of remarkably conserved principles in protein-RNA interactions. These analyses provide a structural basis for interpreting the functional roles of the box C/D sequences in directing specific assembly of box C/D sRNPs.
L7Ae protein, together with fused Nop56/58 (also designated Nop5) and Fibrillarin methyltranferase (FlpA), makes the core of C/D RNP complex in Archaea. It is a homologue of S. cerevisiae Snu13 and mammalian 15.5kD protein. Archaeal L7Ae is also a subunit of H/ACA RNP complex, a subunit of RNase P and one of the ribosomal protein of the 50S subunit. In all cases L7Ae binds to a common kink-turn motif of RNA.