4qyz

Crystal structure of a CRISPR RNA-guided surveillance complex, Cascade, bound to a ssDNA target

spinqualitylabelsall models 4qyz, resolution 3.03Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 4qyz is a 13 chain structure with sequence from Escherichia coli, Escherichia coli K-12 and Escherichia virus Lambda. The January 2015 RCSB PDB Molecule of the Month feature on Cascade and CRISPR by David Goodsell is 10.2210/rcsb_pdb/mom_2015_1. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 3.0303Å Ligands: ZN Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function CSE1_ECOLI CRISPR (clustered regularly interspaced short palindromic repeat), is an adaptive immune system that provides protection against mobile genetic elements (viruses, transposable elements and conjugative plasmids). CRISPR clusters contain sequences complementary to antecedent mobile elements and target invading nucleic acids. CRISPR clusters are transcribed and processed into CRISPR RNA (crRNA). A component of Cascade, which participates in CRISPR interference, the third stage of CRISPR immunity. Cascade binds both crRNA and in a sequence-specific manner negatively supercoiled dsDNA target. This leads to the formation of an R-loop in which the crRNA binds the target DNA, displacing the noncomplementary strand. Cas3 is recruited to Cascade, probably via interactions with CasA, nicks target DNA and then unwinds and cleaves the target, leading to DNA degradation and invader neutralization. CasA is not required for formation of Cascade, but probably enhances binding to and subsequent recognition of both target dsDNA and ssDNA. Publication Abstract from PubMed In prokaryotes, RNA derived from type I and type III CRISPR loci direct large ribonucleoprotein complexes to destroy invading bacteriophage and plasmids. In Escherichia coli, this 405-kDa complex is called Cascade. Here, we report the 3.03A crystal structure of Cascade bound to a single-stranded DNA target. The structure reveals that the CRISPR RNA and target strands do not form a double helix but instead adopt an underwound ribbon-like structure. This non-canonical structure is facilitated by rotation of every sixth nucleotide out of the RNA-DNA hybrid and is stabilized by the highly interlocked organization of protein subunits. These studies provide insight into both the assembly and the activity of this complex and suggest a mechanism to enforce fidelity of target binding. Crystal structure of a CRISPR RNA-guided surveillance complex bound to a ssDNA target.,Mulepati S, Heroux A, Bailey S Science. 2014 Aug 14. pii: 1256996. PMID:25123481 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also CRISPR type I-E (Cascade) CRISPR-Cas CRISPR-Cas Part II Endonuclease 3D structures

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