4r7y

Crystal structure of an active MCM hexamer

spinqualitylabelsall models 4r7y, resolution 2.70Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 4r7y is a 2 chain structure with sequence from Pyrococcus furiosus DSM 3638 and Saccharolobus solfataricus P2. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: ADP, CL, MG, ZN Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function Q8U3I4_PYRFU MCM_SACS2 Presumptive replicative helicase. Has ATPase and DNA helicase activities. The latter preferentially melts 5'-tailed oligonucleotides and is stimulated by the SSB protein (single-stranded DNA binding protein). The active ATPase sites in the MCM ring are formed through the interaction surfaces of two neighboring subunits such that a critical structure of a conserved arginine finger motif is provided in trans relative to the ATP-binding site of the Walker A box of the adjacent subunit. The helicase function is proposed to use a partially sequential mode of ATP hydrolysis; the complex appears to tolerate multiple catalytically inactive subunits. Publication Abstract from PubMed In a previous Research article (<xref>Froelich et al., 2014</xref>), we suggested an MCM helicase activation mechanism, but were limited in discussing the ATPase domain because it was absent from the crystal structure. Here we present the crystal structure of a nearly full-length MCM hexamer that is helicase-active and thus has all features essential for unwinding DNA. The structure is a chimera of Sulfolobus solfataricus N-terminal domain and Pyrococcus furiosus ATPase domain. We discuss three major findings: 1) a novel conformation for the A-subdomain that could play a role in MCM regulation; 2) interaction of a universally conserved glutamine in the N-terminal Allosteric Communication Loop with the AAA+ domain helix-2-insert (h2i); and 3) a recessed binding pocket for the MCM ssDNA-binding motif influenced by the h2i. We suggest that during helicase activation, the h2i clamps down on the leading strand to facilitate strand retention and regulate ATP hydrolysis. Analysis of the crystal structure of an active MCM hexamer.,Miller JM, Arachea BT, Epling LB, Enemark EJ Elife. 2014 Sep 29;3. doi: 10.7554/eLife.03433. PMID:25262915 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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