Crystal structure of the CRISPR RNA–guided surveillance complex from Escherichia coli
Jackson, R.N. ; Golden, S.M. ; Erp, P.B. ; Carter, J. ; Westra, E.R. ; Brouns, S.J.J. ; Oost, J. van der; Terwilliger, T.C. ; Read, R.J. ; Wiedenheft, B. - \ 2014
Science 345 (2014)6203. - ISSN 0036-8075 - p. 1473 - 1479.
bacterial immune-system - processes pre-crrna - thermus-thermophilus - cas systems - interference complex - target recognition - antiviral defense - seed sequence - dna - cascade
Clustered regularly interspaced short palindromic repeats (CRISPRs) are essential components of RNA-guided adaptive immune systems that protect bacteria and archaea from viruses and plasmids. In Escherichia coli, short CRISPR-derived RNAs (crRNAs) assemble into a 405-kilodalton multisubunit surveillance complex called Cascade (CRISPR-associated complex for antiviral defense). Here we present the 3.24 angstrom resolution x-ray crystal structure of Cascade. Eleven proteins and a 61-nucleotide crRNA assemble into a seahorse-shaped architecture that binds double-stranded DNA targets complementary to the crRNA-guide sequence. Conserved sequences on the 3' and 5' ends of the crRNA are anchored by proteins at opposite ends of the complex, whereas the guide sequence is displayed along a helical assembly of six interwoven subunits that present five-nucleotide segments of the crRNA in pseudo–A-form configuration. The structure of Cascade suggests a mechanism for assembly and provides insights into the mechanisms of target recognition.