Second Messenger cA4Formation within the Composite Csm1 Palm Pocket of Type III-A CRISPR-Cas Csm Complex and Its Release Path.Jia, N., Jones, R., Sukenick, G., Patel, D.J.
(2019) Mol Cell 75: 933-943.e6
- PubMed: 31326272
- DOI: https://doi.org/10.1016/j.molcel.2019.06.013
- Primary Citation of Related Structures:
6O73, 6O74, 6O75, 6O78, 6O79, 6O7B, 6O7D, 6O7E, 6O7H, 6O7I
- PubMed Abstract:
Target RNA binding to crRNA-bound type III-A CRISPR-Cas multi-subunit Csm surveillance complexes activates cyclic-oligoadenylate (cA n ) formation from ATP subunits positioned within the composite pair of Palm domain pockets of the Csm1 subunit. The generated cA n 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 (pppA n ), and products (cA n ), to decipher mechanistic aspects of cA n formation and release. A network of intermolecular hydrogen bond alignments accounts for the observed adenosine specificity, with ligand positioning dictating formation of linear pppA n intermediates and subsequent cA n 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 cA n signaling pathway.
Structural Biology Program Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA. Electronic address: email@example.com.