The crystal structure of the CRISPR-associated protein Csn2 from Streptococcus agalactiae

Philipp Ellinger, Zihni Arslan, Reinhild Wurm, Britta Tschapek, Colin MacKenzie, Klaus Pfeffer, Santosh Panjikar, Rolf Wagner, Lutz Schmitt, Holger Gohlke, Ümit Pul, Sander H.J. Smits

Research output: Contribution to journalArticleResearchpeer-review

21 Citations (Scopus)


The prokaryotic immune system, CRISPR, confers an adaptive and inheritable defense mechanism against invasion by mobile genetic elements. Guided by small CRISPR RNAs (crRNAs), a diverse family of CRISPR-associated (Cas) proteins mediates the targeting and inactivation of foreign DNA. Here, we demonstrate that Csn2, a Cas protein likely involved in spacer integration, forms a tetramer in solution and structurally possesses a ring-like structure. Furthermore, co-purified Ca2+ was found important for the DNA binding property of Csn2, which contains a helicase fold, with highly conserved DxD and RR motifs found throughout Csn2 proteins. We could verify that Csn2 binds ds-DNA. In addition molecular dynamics simulations suggested a Csn2 conformation that can "sit" on the DNA helix and binds DNA in a groove on the outside of the ring.

Original languageEnglish
Pages (from-to)350-362
Number of pages13
JournalJournal of Structural Biology
Issue number3
Publication statusPublished - Jun 2012
Externally publishedYes


  • Cas
  • DNA binding
  • MD-simulation
  • PolDom
  • Spacer integration
  • X-ray crystallography

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