Journal
JOURNAL OF MOLECULAR BIOLOGY
Volume 371, Issue 5, Pages 1141-1150Publisher
ACADEMIC PRESS LTD ELSEVIER SCIENCE LTD
DOI: 10.1016/j.jmb.2007.06.029
Keywords
structure of nop56/58-fibrillarin; box C/D RNPs; ribosome biogenesis; RNA methyltransferase; noncoding RNA
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Funding
- NIGMS NIH HHS [R01 GM066958, R01 GM54682, R01 GM66958-01] Funding Source: Medline
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The Nop56/58-fibrillarin heterocomplex is a core protein complex of the box C/D ribonucleoprotein particles that modify and process ribosomal RNAs. The previous crystal structure of the Archaeoglobus fidgidus complex revealed a symmetric dimer of two Nop56/58-fibrillarin complexes linked by the coiled-coil domains of the Nop56/68 proteins. However, because the A. fulgidus Nop56/58 protein lacks some domains found in most other species, it was thought that the bipartite architecture of the heterocomplex was not likely a general phenomenon. Here we report the crystal structure of the Nop56/58-fibrillarin complex bound with methylation cofactor, S-adenosyl-L-methionine from Pyrococcus furiosus, at 2.7 A. The new complex confirms the generality of the previously observed bipartite arrangement. In addition however, the conformation of Nop56/58 in the new structure differs substantially from that in the earlier structure. The distinct conformations of Nop56/58 suggest potential flexibility in Nop56/ 58. Computational normal mode analysis supports this view. Importantly, fibrillarin is repositioned within the two complexes. We propose that hinge motion within Nop56/58 has important implications for the possibility of simultaneously positioning two catalytic sites at the two target sites of a bipartite box C/D guide RNA. (c) 2007 Elsevier Ltd. All rights reserved.
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