3w2v
Crystal structure of the Cmr2dHD-Cmr3 subcomplex bound to 3'-AMP
Structural highlights
FunctionCMR2_PYRFU 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), formerly called psiRNA (prokaryotic silencing) in this organism. Part of the Cmr ribonucleoprotein complex which has divalent cation-dependent endoribonuclease activity specific for ssRNA complementary to the crRNA, generating 5' hydroxy- and 3' phosphate or 2'-3' cyclic phosphate termini. It is not known which subunit has endoribonuclease activity. Cmr complex does not cleave ssDNA complementary to the crRNA. Cleavage of invading RNA is guided by the crRNA; substrate cleavage occurs a fixed distance (14 nt) from the 3' end of the crRNA. In vitro reconstitution shows Cmr1-2 and Cmr5 are not necessary for cleavage. Probably not the subunit that cleaves pre-crRNA, as mutation of numerous metal-binding residues have no effect on cleavage by assembled complex.[1] Publication Abstract from PubMedClustered, regularly interspaced, short palindromic repeat (CRISPR) loci found in prokaryotes are transcribed to produce CRISPR RNAs (crRNAs) that, together with CRISPR-associated (Cas) proteins, target and degrade invading genetic materials. Cmr proteins (Cmr1-6) and crRNA form a sequence-specific RNA silencing effector complex. Here, we report the crystal structures of the Pyrococcus furiosus Cmr2-Cmr3 subcomplex bound with nucleotides (3'-AMP or ATP). The association of Cmr2 and Cmr3 forms an idiosyncratic crevasse, which binds the nucleotides. Cmr3 shares structural similarity with Cas6, which cleaves precursor crRNA for maturation, suggesting the divergent evolution of these proteins. Due to the structural resemblance, the properties of the RNA binding surface observed in Cas6 are well conserved in Cmr3, indicating the RNA binding ability of Cmr3. This surface of Cmr3 constitutes the crevasse observed in the Cmr2-Cmr3 complex. Our findings suggest that the Cmr2-Cmr3 complex uses the crevasse to bind crRNA and/or substrate RNA during the reaction. Crystal Structure of the Cmr2-Cmr3 Subcomplex in the CRISPR-Cas RNA Silencing Effector Complex.,Osawa T, Inanaga H, Numata T J Mol Biol. 2013 Oct 23;425(20):3811-3823. doi: 10.1016/j.jmb.2013.03.042. Epub, 2013 Apr 10. PMID:23583914[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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