2i8e
Structure of SSO1404, a predicted DNA repair-associated protein from Sulfolobus solfataricus P2
Structural highlights
FunctionCAS2A_SACS2 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). Involved in the integration of spacer DNA into the CRISPR cassette (By similarity). Functions as a ssRNA-specific endoribonuclease, producing a 5'-phosphomonoester and a 3'-hydroxy. Does not process pre-crRNA in the manner expected if it were the CRISPR-processing endoribonuclease. Prefers U-rich substrates and often cuts between adjacent U residues in regions predicted to be single-stranded. RNAs as short as 10 residues can serve as substrate.[1] 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 PubMedClustered regularly interspaced short palindromic repeats (CRISPRs) together with the associated CAS proteins protect microbial cells from invasion by foreign genetic elements using presently unknown molecular mechanisms. All CRISPR systems contain proteins of the CAS2 family, suggesting that these uncharacterized proteins play a central role in this process. Here we show that the CAS2 proteins represent a novel family of endoribonucleases. Six purified CAS2 proteins from diverse organisms cleaved single-stranded RNAs preferentially within U-rich regions. A representative CAS2 enzyme, SSO1404 from Sulfolobus solfataricus, cleaved the phosphodiester linkage on the 3'-side and generated 5'-phosphate- and 3'-hydroxyl-terminated oligonucleotides. The crystal structure of SSO1404 was solved at 1.6A resolution revealing the first ribonuclease with a ferredoxin-like fold. Mutagenesis of SSO1404 identified six residues (Tyr-9, Asp-10, Arg-17, Arg-19, Arg-31, and Phe-37) that are important for enzymatic activity and suggested that Asp-10 might be the principal catalytic residue. Thus, CAS2 proteins are sequence-specific endoribonucleases, and we propose that their role in the CRISPR-mediated anti-phage defense might involve degradation of phage or cellular mRNAs. A novel family of sequence-specific endoribonucleases associated with the clustered regularly interspaced short palindromic repeats.,Beloglazova N, Brown G, Zimmerman MD, Proudfoot M, Makarova KS, Kudritska M, Kochinyan S, Wang S, Chruszcz M, Minor W, Koonin EV, Edwards AM, Savchenko A, Yakunin AF J Biol Chem. 2008 Jul 18;283(29):20361-71. Epub 2008 May 15. PMID:18482976[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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