Protein Summary

Nep1 from Saccharomyces cerevisiae

Full name: Ribosomal RNA small subunit methyltransferase NEP1
Synonym: Emg1
GI: 6323215
Orf: L9470.5
COG: COG1756
UniProt: Q06287
Structures: | 3BBD | 3BBE | 3BBH |
Enzyme type: methyltransferase
Position of modification - modification: s:1191(966) - m1Y


Nep1 catalyzes the SAM-dependent methylation of a pseudouridine residue in the loop of hairpin 35 of 18S rRNA (position 1191 = position 966 in E.coli 16 rRNA, normally filled by m2G966 catalyzed by E. coli RsmD). Methylation occurs after the target U is first transformed into Y by a H/ACA RNP (snR35/Cbj5) pseudouridylation system. Yeast nucleolar Nep1 (formerly named Ermg1) is a homolog of Methanocaldococcus jannaschii Nep1 (Archaea). However, in naturally occurring 18S rRNA of Saccharomyces carsbergensis (and probably also S. cerevisiae), m1acp3Y is found, attesting that m1Y1191 is normally further hypermodified by an enzyme that has still to be identified. The crystal structure of Nep1 reveals a fold which is very similar to the conserved core fold of the SPOUT-class methyltransferases superfamily, including Nep1 of M. jannaschii. This highly conserved eukaryotic nucleolar protein Nep1 plays an essential role in 18S rRNA processing and ribosome biogenesis. It binds to a consensus 6-nt RNA-binding motif found in yeast 18S rRNA and facilitates the incorporation of ribosomal protein Rps19 during the formation of pre-ribosomes.

Protein sequence:


Enzymatic activities

Reaction Substrate Type Position
Y:m1Y rRNA (r) SSU/18S/cytosolic None


Title Authors Journal Details PubMed Id DOI
The crystal structure of Nep1 reveals an extended SPOUT-class methyltransferase fold and a pre-organized SAM-binding site. Taylor AB, Meyer B, Leal BZ, Kotter P, Schirf V, Demeler B, Hart PJ, Entian KD, Wohnert J Nucleic Acids Res [details] 18208838 -
The yeast ribosome synthesis factor Emg1 is a novel member of the superfamily of alpha/beta knot fold methyltransferases. Leulliot N, Bohnsack MT, Graille M, Tollervey D, Van Tilbeurgh H Nucleic Acids Res [details] 18063569 -



Last modification of this entry: 2012-07-03 17:24:24.740421
Edited by a user: magda
Edited content: Changed protein_sequence, if_enzyme and enzyme_type.