Summary information and primary citation
- PDB-id
- 7utn; SNAP-derived features in text and JSON formats;
DNAproDB
- Class
- RNA binding protein-RNA-DNA
- Method
- cryo-EM (2.74 Å)
- Summary
- Iscb and wrna bound to target DNA
- Reference
- Schuler G, Hu C, Ke A (2022): "Structural basis for RNA-guided DNA cleavage by IscB-omega RNA and mechanistic comparison with Cas9." Science, eabq7220. doi: 10.1126/science.abq7220.
- Abstract
- Class 2 CRISPR effectors Cas9 and Cas12 may have evolved from nucleases in IS200/IS605 transposons. IscB is about 2/5 the size of Cas9 but shares similar domain organization. The associated ωRNA plays the combined role of crRNA and tracrRNA to guide dsDNA cleavage. Here we report a 2.78 Å cryo-EM structure of IscB-ωRNA bound to dsDNA target, revealing the architectural and mechanistic similarities between IscB and Cas9 RNPs. Target-adjacent motif recognition, R-loop formation, and DNA cleavage mechanisms are explained at high resolution. ωRNA plays the equivalent function of REC domains in Cas9, and contacts the RNA/DNA heteroduplex. The IscB-specific PLMP domain is dispensable for RNA-guided DNA cleavage. The transition from ancestral IscB to Cas9 involved dwarfing the ωRNA and introducing protein domain replacements.
