Structure of the Saccharolobus solfataricus type III-D CRISPR effector

Giuseppe Cannone, Dmytro Kompaniiets, Shirley Graham, Malcolm White*, Laura Spagnolo*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


CRISPR-Cas is a prokaryotic adaptive immune system, classified into six different types, each characterised by a signature protein. Type III systems, classified based on the presence of a Cas10 subunit, are rather diverse multi- subunit assemblies with a range of enzymatic activities and downstream ancillary effectors. The broad array of current biotechnological CRISPR applications is mainly based on proteins classified as Type II, however recent developments established the feasibility and efficacy of multi-protein Type III CRISPR-Cas effector complexes as RNA-targeting tools in eukaryotes. The crenarchaeon Saccharolobus solfataricus has two type III system subtypes (III- B and III-D). Here, we report the cryo-EM structure of the Csm Type III-D complex from S. solfataricus (SsoCsm), which uses CRISPR RNA to bind target RNA molecules, activating the Cas10 subunit for antiviral defence. The structure reveals the complex organisation, subunit/subunit connectivity and protein/guide RNA interactions of the SsoCsm complex, one of the largest CRISPR effectors known.
Original languageEnglish
Article number100098
Number of pages8
JournalCurrent Research in Structural Biology
Early online date6 Feb 2023
Publication statusPublished - 20 Feb 2023


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