New page: ==GPN-loop GTPase Npa3 in complex with GMPPCP== <StructureSection load='5hcn' size='340' side='right' caption='5hcn, resolution 2.20Å' scene=''> == Structural high... |
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Structural highlights
Function[GPN1_YEAST] Small GTPase required for proper nuclear import of RNA polymerase II (RNAPII) (PubMed:20855544, PubMed:21844196). May act at an RNAP assembly step prior to nuclear import (PubMed:23267056). Promotes sister chromatid separation during anaphase (PubMed:21532343).[1] [2] [3] [4] [5] Publication Abstract from PubMedBiogenesis of the 12-subunit RNA polymerase II (Pol II) transcription complex requires so-called GPN-loop GTPases, but the function of these enzymes is unknown. Here we report the first crystal structure of a eukaryotic GPN-loop GTPase, the S. cerevisiae enzyme Npa3 (a homolog of human GPN1, also called RPAP4, XAB1, MBDin), and analyze its catalytic mechanism. The enzyme was trapped in a GDP-bound, closed conformation, and in a novel GTP analogue-bound, open conformation displaying a conserved hydrophobic pocket distant from the active site. We show that Npa3 has chaperone activity and interacts with hydrophobic peptide regions of Pol II subunits that form interfaces in the assembled Pol II complex. Biochemical results are consistent with a model that the hydrophobic pocket binds peptides, and that this can allosterically stimulate GTPase activity and subsequent peptide release. These results suggest that GPN-loop GTPases are assembly chaperones for Pol II and other protein complexes. Structure of GPN-loop GTPase Npa3 and implications for RNA polymerase II assembly.,Niesser J, Wagner FR, Kostrewa D, Muhlbacher W, Cramer P Mol Cell Biol. 2015 Dec 28. pii: MCB.01009-15. PMID:26711263[6] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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