5FSH

Crystal structure of Thermus thermophilus Csm6


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.30 Å
  • R-Value Free: 0.244 
  • R-Value Work: 0.219 
  • R-Value Observed: 0.220 

wwPDB Validation   3D Report Full Report


This is version 1.1 of the entry. See complete history


Literature

Structural Basis for the Endoribonuclease Activity of the Type III-A Crispr-Associated Protein Csm6.

Niewoehner, O.Jinek, M.

(2016) RNA 22: 318

  • DOI: https://doi.org/10.1261/rna.054098.115
  • Primary Citation of Related Structures:  
    5FSH

  • PubMed Abstract: 

    Prokaryotic CRISPR-Cas systems provide an RNA-guided mechanism for genome defense against mobile genetic elements such as viruses and plasmids. In type III-A CRISPR-Cas systems, the RNA-guided multisubunit Csm effector complex targets both single-stranded RNAs and double-stranded DNAs. In addition to the Csm complex, efficient anti-plasmid immunity mediated by type III-A systems also requires the CRISPR-associated protein Csm6. Here we report the crystal structure of Csm6 from Thermus thermophilus and show that the protein is a ssRNA-specific endoribonuclease. The structure reveals a dimeric architecture generated by interactions involving the N-terminal CARF and C-terminal HEPN domains. HEPN domain dimerization leads to the formation of a composite ribonuclease active site. Consistently, mutations of invariant active site residues impair catalytic activity in vitro. We further show that the ribonuclease activity of Csm6 is conserved across orthologs, suggesting that it plays an important functional role in CRISPR-Cas systems. The dimer interface of the CARF domains features a conserved electropositive pocket that may function as a ligand-binding site for allosteric control of ribonuclease activity. Altogether, our work suggests that Csm6 proteins provide an auxiliary RNA-targeting interference mechanism in type III-A CRISPR-Cas systems that operates in conjunction with the RNA- and DNA-targeting endonuclease activities of the Csm effector complex.


  • Organizational Affiliation

    Department of Biochemistry, University of Zurich, Zurich CH-8057, Switzerland.


Macromolecules
Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
CSM6
A, B
467Thermus thermophilus HB8Mutation(s): 0 
UniProt
Find proteins for Q53W17 (Thermus thermophilus (strain ATCC 27634 / DSM 579 / HB8))
Explore Q53W17 
Go to UniProtKB:  Q53W17
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ53W17
Sequence Annotations
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  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.30 Å
  • R-Value Free: 0.244 
  • R-Value Work: 0.219 
  • R-Value Observed: 0.220 
  • Space Group: P 21 21 2
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 95.309α = 90
b = 207.07β = 90
c = 58.903γ = 90
Software Package:
Software NamePurpose
PHENIXrefinement
SLSdata reduction
Aimlessdata scaling
PHENIXphasing

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2016-01-27
    Type: Initial release
  • Version 1.1: 2016-03-02
    Changes: Database references