Cas endonuclease and guide rna variants with improved efficiency

An engineered Cas polypeptide, comprising:

• (a) a sequence having 90% amino acid sequence identity to SEQ ID NO:14 a C-terminal tri-split RuvC domain and three zinc finger motifs;
• and
• (b) one or more of the following amino acids at positions relative to an alignment with SEQ ID NO:14:
• Glutamate at 34, Alanine at 36, Serine at 45, Aspartate at 54, Serine at 77, Glutamate at 81, or Glutamine at 85;
• wherein the engineered Cas polypeptide does not comprise at least one of the following amino acids at positions relative to an alignment with SEQ ID NO:14:
• Phenylalanine at position 38, Alanine at position 40, Histidine at position 79, Alanine at relative position 87, Threonine at relative position 335, Cysteine at position 409, Glutamate at position 421, Lysine at position 467, or Glutamate at position 468 and wherein the engineered Cas polypeptide is capable of site specifically binding a target site of a polynucleotide.

A system comprising a Cas polypeptide and an engineered guide RNA (egRNA), wherein the egRNA is based on a template guide RNA sequence (sgRNA) that comprises a Cas polypeptide recognition domain and wherein the egRNA comprises (i) a deletion, substitution or an insertion at one or more of nucleotide positions 1-3, 3-5, 5-7, 7-9, 59-61, 61-63, 63-65, 147-149, 149-151, 151-153, 153-155, 157-159, 159-161, 163-165, or 167-169 of the sgRNA Cas polypeptide recognition domain or (ii) one of SEQ ID NOs:

• 62-156, SEQ ID NOs:
• 192-207, SEQ ID NOs:
• 260-284, SEQ ID NOs:
• 324-327, SEQ ID NOs:
• 346-355, or SEQ ID NO:362.