CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) and associated Cas proteins comprise a system for heritable host defense by prokaryotic cells against phage and other foreign DNA; Protein of this family often fused to HTH domain; Some proteins could have an additional fusion with RecB-family nuclease domain; Core domain appears to have a Rossmann-like fold; loosely associated with CRISPR/Cas systems; also known as NE0113 family