Structure of a CRISPR‐associated protein Cas2 from Desulfovibrio vulgaris
CRISPRs (clustered regularly interspaced short palindromic repeats) provide bacteria and archaea with RNA‐guided acquired immunity to invasive DNAs. CRISPR‐associated (Cas) proteins carry out the immune effector functions. Cas2 is a universal component of the CRISPR system. Here, a 1.35 Å resolution crystal structure of Cas2 from the bacterium Desulfovibrio vulgaris (DvuCas2) is reported. DvuCas2 is a homodimer, with each protomer consisting of an N‐terminal βαββαβ ferredoxin fold (amino acids 1–78) to which is appended a C‐terminal segment (amino acids 79–102) that includes a short 310‐helix and a fifth β‐strand. The β5 strands align with the β4 strands of the opposite protomers, resulting in two five‐stranded antiparallel β‐sheets that form a sandwich at the dimer interface. The DvuCas2 dimer is stabilized by a distinctive network of hydrophilic cross‐protomer side‐chain interactions.
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