Gene content similarity between type I-E and type III-A systems and structural organization of large subunits of different CRISPR-Cas systems of type I and III. A. Genes in the operons for I-E and III-A subtypes are shown by arrows with size roughly proportion to the size of the corresponding gene. Homologous genes are shown by the arrows of same color or hashing. RAMPs are shown by pink or pink hashing. Solid lines connect genes for which homology can be confidently demonstrated, and dashed lines connect genes for which homology is inferred tentatively. The Cascade complex subunits are shown by square brackets. Two previously published domain annotations are included for comparison. B. Domain organization of large subunits of different type I and III CRISPR-Cas systems. Domain size is roughly proportional to correspondent sequence length. The letter "S" marks the regions that could be homologous to small subunits of Cascade complex encoded as separated genes in Type III systems, I-E subtype and some systems of I-A subtype.