Summary information and primary citation

PDB-id
5ds4; DSSR-derived features in text and JSON formats
Class
hydrolase-DNA
Method
X-ray (3.2 Å)
Summary
Crystal structure the escherichia coli cas1-cas2 complex bound to protospacer DNA
Reference
Nunez JK, Harrington LB, Kranzusch PJ, Engelman AN, Doudna JA (2015): "Foreign DNA capture during CRISPR-Cas adaptive immunity." Nature, 527, 535-538. doi: 10.1038/nature15760.
Abstract
Bacteria and archaea generate adaptive immunity against phages and plasmids by integrating foreign DNA of specific 30-40-base-pair lengths into clustered regularly interspaced short palindromic repeat (CRISPR) loci as spacer segments. The universally conserved Cas1-Cas2 integrase complex catalyses spacer acquisition using a direct nucleophilic integration mechanism similar to retroviral integrases and transposases. How the Cas1-Cas2 complex selects foreign DNA substrates for integration remains unknown. Here we present X-ray crystal structures of the Escherichia coli Cas1-Cas2 complex bound to cognate 33-nucleotide protospacer DNA substrates. The protein complex creates a curved binding surface spanning the length of the DNA and splays the ends of the protospacer to allow each terminal nucleophilic 3'-OH to enter a channel leading into the Cas1 active sites. Phosphodiester backbone interactions between the protospacer and the proteins explain the sequence-nonspecific substrate selection observed in vivo. Our results uncover the structural basis for foreign DNA capture and the mechanism by which Cas1-Cas2 functions as a molecular ruler to dictate the sequence architecture of CRISPR loci.

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