Crystal structure of the largest subunit of a bacterial RNA-guided immune complex and its role in DNA target binding

Sabin Mulepati, Amberly Orr, Scott Bailey

Research output: Contribution to journalArticlepeer-review

Abstract

Prokaryotes make use of small RNAs encoded by CRISPR (clustered regularly interspaced short palindromic repeat) loci to provide immunity against bacteriophage or plasmid invasion. In Escherichia coli, the CRISPR-associated complex for antiviral defense (Cascade) utilizes these RNAs to target foreignDNAfor destruction. CasA, the largest subunit of Cascade, is essential for its function. Here we report the crystal structure of Thermus thermophilus CasA. The structure is composed of two domains that are arranged in a chair-like conformation with a novel fold forming the larger N-terminal domain. Docking of the crystal structure into cryo-electron microscopy maps reveals two loops in CasA that likely have important functions in DNA target binding. Finally, DNA binding experiments show that CasA is essential for binding of Cascade to DNA target.

Original languageEnglish (US)
Pages (from-to)22445-22449
Number of pages5
JournalJournal of Biological Chemistry
Volume287
Issue number27
DOIs
StatePublished - Jun 29 2012

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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