4n06
Crystal structure of Cas1 from Archaeoglobus fulgidus and its nucleolytic activity
Structural highlights
FunctionCAS1A_ARCFU 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). Acts as a dsDNA endonuclease. May be involved in the integration of spacer DNA into the CRISPR cassette (By similarity). Publication Abstract from PubMedClustered Regularly Interspaced Short Palindromic Repeats (CRISPRs) and CRISPR-associated (Cas) proteins are involved in bacterial acquired immunity against incoming hazardous genetic materials. Cas1 is ubiquitous in CRISPR-containing microorganisms and supposed to recognize and cleave a foreign nucleic acid, and integrate the cleaved fragment into host genome using a yet unidentified mechanism. However, all the reported Cas1s did not show the nucleolytic activity, which makes its role still obscure. The elucidated crystal structure of Cas1 from Archaeoglobus fulgidus (AfCas1) shows a butterfly-like dimeric structure. The Asp out of three confirmed nucleolytic residues of Glu, His, and Asp in other Cas1s is replaced with Glu in AfCas1. Further, insertion of five residues into one of two loops, which are close to the catalytic center of and disordered in other Cas1 structures, partially covers the active site of AfCas1. Nonetheless, in vitro assays show that its nucleic acid-binding activity was not impaired against the tested single-stranded (ss) DNA, various forms of double-stranded (ds) DNA, or ssRNA with a hydrolyzing activity against ssRNA and dsDNA in a metal ion-dependent way. These results support the proposed Cas1's function at the early step of this bacterial immune system. Crystal structure of Cas1 from Archaeoglobus fulgidus and characterization of its nucleolytic activity.,Kim TY, Shin M, Huynh Thi Yen L, Kim JS Biochem Biophys Res Commun. 2013 Nov 29;441(4):720-5. doi:, 10.1016/j.bbrc.2013.10.122. Epub 2013 Nov 5. PMID:24211577[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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