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Cell Rep. 2014 Dec 11;9(5):1610-1617. doi: 10.1016/j.celrep.2014.11.007. Epub 2014 Dec 4.

Essential structural and functional roles of the Cmr4 subunit in RNA cleavage by the Cmr CRISPR-Cas complex.

Author information

1
Institute of Molecular Biophysics, Florida State University, Tallahassee, FL 32306, USA.
2
Departments of Biochemistry and Molecular Biology, Genetics, and Microbiology, University of Georgia, Athens, GA 30602, USA.
3
Departments of Biochemistry and Molecular Biology, Genetics, and Microbiology, University of Georgia, Athens, GA 30602, USA. Electronic address: mterns@bmb.uga.edu.
4
Institute of Molecular Biophysics, Florida State University, Tallahassee, FL 32306, USA; Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32306, USA. Electronic address: hong.li@fsu.edu.
5
Institute of Molecular Biophysics, Florida State University, Tallahassee, FL 32306, USA; Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32306, USA. Electronic address: sstagg@fsu.edu.

Abstract

The Cmr complex is the multisubunit effector complex of the type III-B clustered regularly interspaced short palindromic repeats (CRISPR)-Cas immune system. The Cmr complex recognizes a target RNA through base pairing with the integral CRISPR RNA (crRNA) and cleaves the target at multiple regularly spaced locations within the complementary region. To understand the molecular basis of the function of this complex, we have assembled information from electron microscopic and X-ray crystallographic structural studies and mutagenesis of a complete Pyrococcus furiosus Cmr complex. Our findings reveal that four helically packed Cmr4 subunits, which make up the backbone of the Cmr complex, act as a platform to support crRNA binding and target RNA cleavage. Interestingly, we found a hook-like structural feature associated with Cmr4 that is likely the site of target RNA binding and cleavage. Our results also elucidate analogies in the mechanisms of crRNA and target molecule binding by the distinct Cmr type III-A and Cascade type I-E complexes.

PMID:
25482566
PMCID:
PMC4269474
DOI:
10.1016/j.celrep.2014.11.007
[Indexed for MEDLINE]
Free PMC Article

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