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Structures of CRISPR Cas3 offer mechanistic insights into Cascade-activated DNA unwinding and degradation.
- Source :
-
Nature Structural & Molecular Biology . Sep2014, Vol. 21 Issue 9, p771-777. 7p. - Publication Year :
- 2014
-
Abstract
- CRISPR drives prokaryotic adaptation to invasive nucleic acids such as phages and plasmids, using an RNA-mediated interference mechanism. Interference in type I CRISPR-Cas systems requires a targeting Cascade complex and a degradation machine, Cas3, which contains both nuclease and helicase activities. Here we report the crystal structures of Thermobifida fusca Cas3 bound to single-stranded (ss) DNA substrate and show that it is an obligate 3′-to-5′ ssDNase that preferentially accepts substrate directly from the helicase moiety. Conserved residues in the HD-type nuclease coordinate two irons for ssDNA cleavage. We demonstrate ATP coordination and conformational flexibility of the SF2-type helicase domain. Cas3 is specifically guided toward Cascade-bound target DNA by a PAM sequence, through physical interactions with both the nontarget substrate strand and the CasA protein. The sequence of recognition events ensures well-controlled DNA targeting and degradation of foreign DNA by Cascade and Cas3. [ABSTRACT FROM AUTHOR]
- Subjects :
- *CRISPRS
*DNA
*PLASMIDS
*CRYSTAL structure
*PROTEINS
Subjects
Details
- Language :
- English
- ISSN :
- 15459993
- Volume :
- 21
- Issue :
- 9
- Database :
- Academic Search Index
- Journal :
- Nature Structural & Molecular Biology
- Publication Type :
- Academic Journal
- Accession number :
- 97944077
- Full Text :
- https://doi.org/10.1038/nsmb.2875