Fig. 2: New class 1 CRISPR–Cas systems.
From: An updated evolutionary classification of CRISPR–Cas systems including rare variants
a, Genetic organization of the recently identified type VII and subtypes III-G, III-H and III-I CRISPR–Cas systems. Homologous domains are colour-coded and identified by a family name. The gene names follow the previous classification12. Protein-coding genes are shown roughly to scale; CRISPR arrays are not shown to scale. In subtypes III-G, III-H and III-I, the Palm domains of Cas10 responsible for signalling-molecule synthesis are inactivated. The organism and the corresponding gene range are shown in grey on the right of the loci. If genes are not present in every locus of the respective systems, they are shown by dashed outlines. In the type III-G schematic, the question mark next to Csx26 indicates that the assignment of this protein as a Cas11 counterpart remains hypothetical. b, Schematic representation of CRISPR–Cas effector complexes of type VII and subtypes III-D, III-E, III-G, III-H and III-I. The type VII, subtype III-D1 and III-E schematics are based on the solved structures (Protein Data Bank (PDB) identifiers 8zwl, 8bww and 7y82, respectively). The schematics for subtypes III-G and III-H are based on AlphaFold3 complex models using the following proteins and RNAs: III-G (NC_012623.1, Sulfolobus islandicus Y.N.15.51): 6×Cas7 (most 5′), 1×Cas7 (between csx26 and cas10), 5×Csx26, 1×Cas5, 1×Cas10, crRNA (48 nucleotides (nt)); III-H (RPGO01000026 ‘Candidatus Argoarchaeum ethanivorans’, AEth_01085): 7×Cas7, 1×Cas5, 1×Cas10, crRNA is the same as for III-G; III-I (Desulfonema magnum WP_207677910 and WP_207677911.1): 1×Cas7-11i, 1×Cas10, crRNA is from type III-E of D. magnum (PDB 7zol). AlphaFold3 interface predicted template modelling scores: III-G, 0.52; III-H, 0.59; III-I, 0.75. The black line schematically represents crRNA. Full models in Extended Data Fig. 5. c, Genomic locus organization of type I and type IV variants that acquired a new nuclease domain and/or lost Cas3 helicase-nuclease. Designations are as in a. d, Genomic locus organization of new Tn7 and Mu transposon-associated type I CRISPR–Cas variants. The tns and tni genes encode transposase subunits. Designations are as in a. e, Genomic locus organization of new type III variants. Designations are as in a. PD-(D/E)xK, nuclease of the respective superfamilies; TPR, tetratricopeptide repeats; STAND, signal transduction ATPases with numerous domains; NTD, N-terminal domain; CTD, C-terminal domain.
