3egi
Methyltransferase domain of human trimethylguanosine synthase TGS1 bound to m7GpppA (inactive form)
Structural highlights
FunctionTGS1_HUMAN Catalyzes the 2 serial methylation steps for the conversion of the 7-monomethylguanosine (m(7)G) caps of snRNAs and snoRNAs to a 2,2,7-trimethylguanosine (m(2,2,7)G) cap structure. The enzyme is specific for guanine, and N7 methylation must precede N2 methylation. Hypermethylation of the m7G cap of U snRNAs leads to their concentration in nuclear foci, their colocalization with coilin and the formation of canonical Cajal bodies (CBs). Plays a role in transcriptional regulation.[1] [2] [3] [4] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedMethyltransferases play an important role in the post-transcriptional maturation of most ribonucleic acids. The modification of spliceosomal UsnRNAs includes N2-dimethylation of the m(7)G cap catalyzed by trimethylguanosine synthase 1 (TGS1). This 5'-cap hypermethylation occurs during the biogenesis of UsnRNPs as it initiates the m(3)G cap-dependent nuclear import of UsnRNPs. The conserved methyltransferase domain of human TGS1 has been purified, crystallized and the crystal structure of this domain with bound substrate m(7)GpppA was solved by means of multiple-wavelength anomalous dispersion. Crystal structure analysis revealed that m(7)GpppA binds via its adenosine moiety to the structurally conserved adenosylmethionine-binding pocket, while the m(7) guanosine remains unbound. This unexpected binding only occurs in the absence of AdoMet and suggests an incomplete binding pocket for the m(7)G cap which is caused by the N-terminal truncation of the protein. These structural data are consistent with the finding that the crystallized fragment of human TGS1 is catalytically inactive, while a fragment that is 17 amino acids longer exhibits activity. Structure analysis of the conserved methyltransferase domain of human trimethylguanosine synthase TGS1.,Monecke T, Dickmanns A, Strasser A, Ficner R Acta Crystallogr D Biol Crystallogr. 2009 Apr;65(Pt 4):332-8. Epub 2009 Mar 19. PMID:19307714[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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