8Z0L

Cryo-EM structure of Cas8-HNH system at partial R-loop state

Summary for 8Z0L

• Entry DOI: 10.2210/pdb8z0l/pdb
• EMDB information: 39707
• Descriptor: type I-F CRISPR-associated protein Csy3, hypothetical protein J6N51_11000, HNH endonuclease, ... (7 entities in total)
• Functional Keywords: a protein complex, antiviral protein/dna/rna, antiviral protein-dna-rna complex
• Biological source: Selenomonas sp.; More
• Total number of polymer chains: 12
• Total formula weight: 349100.43

Authors

Zhang, H.,Zhu, H.,Li, X.,Liu, Y. (deposition date: 2024-04-09, release date: 2024-10-02, Last modification date: 2024-10-30)

Primary citation

Li, X.,Liu, Y.,Han, J.,Zhang, L.,Liu, Z.,Wang, L.,Zhang, S.,Zhang, Q.,Fu, P.,Yin, H.,Zhu, H.,Zhang, H.
Structural basis for the type I-F Cas8-HNH system.
Embo J., 43:4656-4667, 2024

PubMed Abstract: The Cas3 nuclease is utilized by canonical type I CRISPR-Cas systems for processive target DNA degradation, while a newly identified type I-F CRISPR variant employs an HNH nuclease domain from the natural fusion Cas8-HNH protein for precise target cleavage both in vitro and in human cells. Here, we report multiple cryo-electron microscopy structures of the type I-F Cas8-HNH system at different functional states. The Cas8-HNH Cascade complex adopts an overall G-shaped architecture, with the HNH domain occupying the C-terminal helical bundle domain (HB) of the Cas8 protein in canonical type I systems. The Linker region connecting Cas8-NTD and HNH domains adopts a rigid conformation and interacts with the Cas7.6 subunit, enabling the HNH domain to be in a functional position. The full R-loop formation displaces the HNH domain away from the Cas6 subunit, thus activating the target DNA cleavage. Importantly, our results demonstrate that precise target cleavage is dictated by a C-terminal helix of the HNH domain. Together, our work not only delineates the structural basis for target recognition and activation of the type I-F Cas8-HNH system, but also guides further developments leveraging this system for precise DNA editing.

PubMed: 39251884
DOI: 10.1038/s44318-024-00229-8

Experimental method

ELECTRON MICROSCOPY (2.57 Å)