Second messenger cA(4) formation within the composite Csm1 palm pocket of type III-A CRISPR-Cas Csm complex and its release path Journal Article


Authors: Jia, N.; Jones, R.; Sukenick, G.; Patel, D. J.
Article Title: Second messenger cA(4) formation within the composite Csm1 palm pocket of type III-A CRISPR-Cas Csm complex and its release path
Abstract: Target RNA binding to crRNA-bound type III-A CRISPR-Cas multi-subunit Csm surveillance complexes activates cyclic-oligoadenylate (cAn) formation from ATP subunits positioned within the composite pair of Palm domain pockets of the Csm1 subunit. The generated cAn second messenger in turn targets the CARF domain of trans-acting RNase Csm6, triggering its HEPN domain-based RNase activity. We have undertaken cryo-EM studies on multi-subunit Thermococcus onnurineus Csm effector ternary complexes, as well as X-ray studies on Csm1–Csm4 cassette, both bound to substrate (AMPPNP), intermediates (pppAn), and products (cAn), to decipher mechanistic aspects of cAn formation and release. A network of intermolecular hydrogen bond alignments accounts for the observed adenosine specificity, with ligand positioning dictating formation of linear pppAn intermediates and subsequent cAn formation by cyclization. We combine our structural results with published functional studies to highlight mechanistic insights into the role of the Csm effector complex in mediating the cAn signaling pathway. © 2019 Elsevier Inc. Cryo-EM and X-ray studies on type III-A CRISPR-Cas Csm ternary complexes bound to substrates (AMPPNP and ATP), intermediates (pppAn), and products (cAn) provide mechanistic insights into recognition of adenosine-specific substrates, positioning of linear pppAn intermediates, and subsequent cyclized cAn products, as well as an inter-subunit pathway for cAn products release. © 2019 Elsevier Inc.
Keywords: adenosine recognition specificity; atp conversion into pppan intermediates and can products; ligand positioning in composite palm pocket; mechanistic insights into ca4 formation and release; type iii-a crispr-cas csm
Journal Title: Molecular Cell
Volume: 75
Issue: 5
ISSN: 1097-2765
Publisher: Cell Press  
Date Published: 2019-09-05
Start Page: 933
End Page: 943.e6
Language: English
DOI: 10.1016/j.molcel.2019.06.013
PUBMED: 31326272
PROVIDER: scopus
PMCID: PMC6731140
DOI/URL:
Notes: Source: Scopus
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  1. Dinshaw J Patel
    424 Patel
  2. Ning Jia
    5 Jia