RNA Targeting by the Type III-A CRISPR-Cas Csm Complex of Thermus thermophilus

R.H.J. Staals, Y. Zhu, D.W. Taylor, J.E. Kornfeld, K. Sharma, A. Barendregt, J.J. Koehorst, M. Vlot, N. Neupane, K. Varossieau, K. Sakamoto, T. Suzuki, P.J. Schaap, H. Urlaub, A.J.R. Heck, E. Nogales, J.A. Doudna, A. Shinkai, J. van der Oost

Research output: Contribution to journalArticleAcademicpeer-review

142 Citations (Scopus)


CRISPR-Cas is a prokaryotic adaptive immune system that provides sequence-specific defense against foreign nucleic acids. Here we report the structure and function of the effector complex of the Type III-A CRISPR-Cas system of Thermus thermophilus: the Csm complex (TtCsm). TtCsm is composed of five different protein subunits (Csm1–Csm5) with an uneven stoichiometry and a single crRNA of variable size (35–53 nt). The TtCsm crRNA content is similar to the Type III-B Cmr complex, indicating that crRNAs are shared among different subtypes. A negative stain EM structure of the TtCsm complex exhibits the characteristic architecture of Type I and Type III CRISPR-associated ribonucleoprotein complexes. crRNA-protein crosslinking studies show extensive contacts between the Csm3 backbone and the bound crRNA. We show that, like TtCmr, TtCsm cleaves complementary target RNAs at multiple sites. Unlike Type I complexes, interference by TtCsm does not proceed via initial base pairing by a seed sequence.
Original languageEnglish
Pages (from-to)518-530
JournalMolecular Cell
Issue number4
Publication statusPublished - 2014


  • guided surveillance complex
  • bacterial immune-system
  • adaptive immunity
  • mass-spectrometry
  • crystal-structure
  • escherichia-coli
  • haloferax-volcanii
  • antiviral defense
  • seed sequence
  • protein

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