4r5q

Structural highlights

Function

CAS4_PYRCJ CRISPR (clustered regularly interspaced short palindromic repeat) is an adaptive immune system that provides protection against mobile genetic elements (viruses, transposable elements and conjugative plasmids). CRISPR clusters contain sequences complementary to antecedent mobile elements and target invading nucleic acids. CRISPR clusters are transcribed and processed into CRISPR RNA (crRNA). A ssDNA exonuclease that has 5' to 3' activity, yielding 5'-OH and 3'-phosphate groups. Has Mn(2+)-dependent endonuclease activity on circular ssDNA. Can unwind dsDNA; unwinding does not require ATP.^{[1] [2]}

References

1. ↑ Lemak S, Beloglazova N, Nocek B, Skarina T, Flick R, Brown G, Popovic A, Joachimiak A, Savchenko A, Yakunin AF. Toroidal structure and DNA cleavage by the CRISPR-associated [4Fe-4S] cluster containing Cas4 nuclease SSO0001 from Sulfolobus solfataricus. J Am Chem Soc. 2013 Nov 20;135(46):17476-87. doi: 10.1021/ja408729b. Epub 2013, Nov 11. PMID:24171432 doi:http://dx.doi.org/10.1021/ja408729b
2. ↑ Lemak S, Nocek B, Beloglazova N, Skarina T, Flick R, Brown G, Joachimiak A, Savchenko A, Yakunin AF. The CRISPR-associated Cas4 protein Pcal_0546 from Pyrobaculum calidifontis contains a [2Fe-2S] cluster: crystal structure and nuclease activity. Nucleic Acids Res. 2014;42(17):11144-55. PMID:25200083 doi:10.1093/nar/gku797