The crystal structure of Nep1 reveals an extended SPOUT-class methyltransferase fold and a pre-organized SAM-binding site
Ribosome biogenesis in eukaryotes requires the participation of a large number of ribosome assembly factors. The highly conserved eukaryotic nucleolar protein Nep1 has an essential but unknown function in 18S rRNA processing and ribosome biogenesis. In Saccharomyces cerevisiae the malfunction of a temperature-sensitive Nep1 protein (nep1-1ts) was suppressed by the addition of S-adenosylmethionine (SAM). This suggests the participation of Nep1 in a methyltransferase reaction during ribosome biogenesis. In addition, yeast Nep1 binds to a 6-nt RNA-binding motif also found in 18S rRNA and facilitates the incorporation of ribosomal protein Rps19 during the formation of pre-ribosomes. Here, we present the X-ray structure of the Nep1 homolog from the archaebacterium Methanocaldococcus jannaschii in its free form (2.2 Å resolution) and bound to the S-adenosylmethionine analog S-adenosylhomocysteine (SAH, 2.15 Å resolution) and the antibiotic and general methyltransferase inhibitor sinefungin (2.25 Å resolution). The structure reveals a fold which is very similar to the conserved core fold of the SPOUT-class methyltransferases but contains a novel extension of this common core fold. SAH and sinefungin bind to Nep1 at a preformed binding site that is topologically equivalent to the cofactor-binding site in other SPOUT-class methyltransferases. Therefore, our structures together with previous genetic data suggest that Nep1 is a genuine rRNA methyltransferase.
|Author:||Alexander B. Taylor, Britta Meyer, Belinda Z. Leal, Peter Kötter, Virgil Schirf, Borries Demeler, P. John Hart, Karl-Dieter Entian, Jens Wöhnert|
|Date of Publication (online):||01.10.2008|
|Year of first Publication:||2008|
|Publishing Institution:||Univ.-Bibliothek Frankfurt am Main|
|Source:||Nucleic Acids Research, 2008, Vol. 36, No. 5 1542-1554 doi:10.1093/nar/gkm1172|
|Dewey Decimal Classification:||570 Biowissenschaften; Biologie|
© 2008 The Author(s) This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
|Licence (German):||Veröffentlichungsvertrag für Publikationen ohne Print on Demand|