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Mol Cell. 2013 Oct 10;52(1):135-145. doi: 10.1016/j.molcel.2013.09.013.

Structure and activity of the RNA-targeting Type III-B CRISPR-Cas complex of Thermus thermophilus.

Author information

1
Laboratory of Microbiology, Department of Agrotechnology and Food Sciences, Wageningen University, 6703 HB Wageningen, The Netherlands.
2
RIKEN SPring-8 Center, 679-5148 Hyogo, Japan.
3
Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, CT 06520-8114, USA.
4
California Institute for Quantitative Biosciences, University of California, San Francisco, CA 94158-2330, USA.
5
Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, University of Utrecht, 3584 CH Utrecht, The Netherlands.
6
Laboratory of Systems and Synthetic Biology, Wageningen University, 6703 HB Wageningen, The Netherlands.
7
Global Research Cluster, RIKEN, Saitama 351-0198, Japan.
8
Department of Molecular and Cell Biology, and Howard Hughes Medical Institute, University of California, Berkeley, CA 94720-3200, USA; Physical Biosciences Division, Lawrence Berkeley National Lab, Berkeley, CA 94720-3200, USA.
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Contributed equally

Abstract

The CRISPR-Cas system is a prokaryotic host defense system against genetic elements. The Type III-B CRISPR-Cas system of the bacterium Thermus thermophilus, the TtCmr complex, is composed of six different protein subunits (Cmr1-6) and one crRNA with a stoichiometry of Cmr112131445361:crRNA1. The TtCmr complex copurifies with crRNA species of 40 and 46 nt, originating from a distinct subset of CRISPR loci and spacers. The TtCmr complex cleaves the target RNA at multiple sites with 6 nt intervals via a 5' ruler mechanism. Electron microscopy revealed that the structure of TtCmr resembles a "sea worm" and is composed of a Cmr2-3 heterodimer "tail," a helical backbone of Cmr4 subunits capped by Cmr5 subunits, and a curled "head" containing Cmr1 and Cmr6. Despite having a backbone of only four Cmr4 subunits and being both longer and narrower, the overall architecture of TtCmr resembles that of Type I Cascade complexes.

PMID:
24119403
PMCID:
PMC4006948
DOI:
10.1016/j.molcel.2013.09.013
[Indexed for MEDLINE]
Free PMC Article

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