3i4h | pdb_00003i4h
Crystal structure of Cas6 in Pyrococcus furiosus
Structural highlights
Function[CAS6_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), also called psiRNA (prokaryotic silencing) in this organism. This protein processes pre-crRNA into individual crRNA units, with an 8-nt 5'-repeat DNA tag that may help other proteins recognize the crRNA. Further processing occurs at their 3' termini in this organism. Generates a 5'-hydroxy and 2',3'-cyclic phosphodiester.[1] [2] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedAn RNA-based gene silencing pathway that protects bacteria and archaea from viruses and other genome invaders is hypothesized to arise from guide RNAs encoded by CRISPR loci and proteins encoded by the cas genes. CRISPR loci contain multiple short invader-derived sequences separated by short repeats. The presence of virus-specific sequences within CRISPR loci of prokaryotic genomes confers resistance against corresponding viruses. The CRISPR loci are transcribed as long RNAs that must be processed to smaller guide RNAs. Here we identified Pyrococcus furiosus Cas6 as a novel endoribonuclease that cleaves CRISPR RNAs within the repeat sequences to release individual invader targeting RNAs. Cas6 interacts with a specific sequence motif in the 5' region of the CRISPR repeat element and cleaves at a defined site within the 3' region of the repeat. The 1.8 angstrom crystal structure of the enzyme reveals two ferredoxin-like folds that are also found in other RNA-binding proteins. The predicted active site of the enzyme is similar to that of tRNA splicing endonucleases, and concordantly, Cas6 activity is metal-independent. cas6 is one of the most widely distributed CRISPR-associated genes. Our findings indicate that Cas6 functions in the generation of CRISPR-derived guide RNAs in numerous bacteria and archaea. Cas6 is an endoribonuclease that generates guide RNAs for invader defense in prokaryotes.,Carte J, Wang R, Li H, Terns RM, Terns MP Genes Dev. 2008 Dec 15;22(24):3489-96. PMID:19141480[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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