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; Cas1 is the most universal CRISPR system protein thought to be involved in spacer intergration. Cas1 is metal-dependent deoxyribonuclease, also binds RNA; Shown to possess a unique fold consisting of a N-terminal beta-strand domain and a C-terminal alpha-helical domain.
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