Fuente: WIPO "tomato" Described herein are engineered, non-naturally occurring systems and compositions comprising multimeric CRISPR-Cas complexes comprising a β-CASP polypeptide, a plurality of Cas polypeptides, and a guide molecule, packaging and delivery systems thereof, and methods of use thereof, for modifying target polynucleotides. In addition, described herein are engineered, non-naturally occurring systems and compositions comprising a class of small Cas proteins (Type II-B, II-C, and II-D Cas proteins) and methods of modifying target sequences using the Type II-B, II-C, II-D Cas proteins and systems thereof.