4qu4

Improved refinement of the Mtr4 apo crystal structure

spinqualitylabelsall models 4qu4, resolution 3.39Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 4qu4 is a 1 chain structure. This structure supersedes the now removed PDB entry 3l9o. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: PO4 Activity: RNA helicase, with EC number 3.6.4.13 Resources: FirstGlance, OCA, RCSB, PDBsum Function [MTR4_YEAST] ATP-dependent RNA helicase required for the 3'-end formation of 5.8S RNA. Cofactor for the exosome complex that unwinds secondary structure in pre-rRNA. Required for nucleocytoplasmic transport of mRNA. May serve as a chaperone which translocates or normalizes the structure of mRNAs in preparation for export. Component of the TRAMP complex which has a poly(A) RNA polymerase activity and is involved in a post-transcriptional quality control mechanism limiting inappropriate expression of genetic information. Polyadenylation is required for the degradative activity of the exosome on several of its nuclear RNA substrates. Publication Abstract from PubMed Mtr4 is a conserved Ski2-like RNA helicase and a subunit of the TRAMP complex that activates exosome-mediated 3'-5' turnover in nuclear RNA surveillance and processing pathways. Prominent features of the Mtr4 structure include a four-domain ring-like helicase core and a large arch domain that spans the core. The 'ratchet helix' is positioned to interact with RNA substrates as they move through the helicase. However, the contribution of the ratchet helix in Mtr4 activity is poorly understood. Here we show that strict conservation along the ratchet helix is particularly extensive for Ski2-like RNA helicases compared to related helicases. Mutation of residues along the ratchet helix alters in vitro activity in Mtr4 and TRAMP and causes slow growth phenotypes in vivo. We also identify a residue on the ratchet helix that influences Mtr4 affinity for polyadenylated substrates. Previous work indicated that deletion of the arch domain has minimal effect on Mtr4 unwinding activity. We now show that combining the arch deletion with ratchet helix mutations abolishes helicase activity and produces a lethal in vivo phenotype. These studies demonstrate that the ratchet helix modulates helicase activity and suggest that the arch domain plays a previously unrecognized role in unwinding substrates. The Mtr4 ratchet helix and arch domain both function to promote RNA unwinding.,Taylor LL, Jackson RN, Rexhepaj M, King AK, Lott LK, van Hoof A, Johnson SJ Nucleic Acids Res. 2014 Nov 20. pii: gku1208. PMID:25414331 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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