8D3L

Type I-C Cas4-Cas1-Cas2 complex bound to a PAM/PAM prespacer

Summary for 8D3L

• Entry DOI: 10.2210/pdb8d3l/pdb
• EMDB information: 27159 27160 27161 27162
• Descriptor: CRISPR-associated endonuclease Cas1, CRISPR-associated endonuclease Cas2, PAM/PAM strand 2, ... (8 entities in total)
• Functional Keywords: crispr cas adaptation type i-c, hydrolase-dna complex, hydrolase/dna
• Biological source: Alkalihalobacillus halodurans C-125; More
• Total number of polymer chains: 10
• Total formula weight: 251250.49

Authors

Dhingra, Y.,Suresh, S.K.,Juneja, P.,Sashital, D.G. (deposition date: 2022-06-01, release date: 2022-11-02, Last modification date: 2024-06-12)

Primary citation

Dhingra, Y.,Suresh, S.K.,Juneja, P.,Sashital, D.G.
PAM binding ensures orientational integration during Cas4-Cas1-Cas2-mediated CRISPR adaptation.
Mol.Cell, 82:4353-, 2022

PubMed Abstract: Adaptation in CRISPR-Cas systems immunizes bacteria and archaea against mobile genetic elements. In many DNA-targeting systems, the Cas4-Cas1-Cas2 complex is required for selection and processing of DNA segments containing PAM sequences prior to integration of these "prespacer" substrates as spacers in the CRISPR array. We determined cryo-EM structures of the Cas4-Cas1-Cas2 adaptation complex from the type I-C system that encodes standalone Cas1 and Cas4 proteins. The structures reveal how Cas4 specifically reads out bases within the PAM sequence and how interactions with both Cas1 and Cas2 activate Cas4 endonuclease activity. The Cas4-PAM interaction ensures tight binding between the adaptation complex and the prespacer, significantly enhancing integration of the non-PAM end into the CRISPR array and ensuring correct spacer orientation. Corroborated with our biochemical results, Cas4-Cas1-Cas2 structures with substrates representing various stages of CRISPR adaptation reveal a temporally resolved mechanism for maturation and integration of functional spacers into the CRISPR array.

PubMed: 36272411
DOI: 10.1016/j.molcel.2022.09.030

Experimental method

ELECTRON MICROSCOPY (3.49 Å)