EMD-7347

Single-particle
3.66 Å
EMD-7347 Deposition: 17/01/2018
Map released: 27/06/2018
Last modified: 29/11/2023
Overview 3D View Sample Experiment Validation Volume Browser Additional data Links
Overview 3D View Sample Experiment Validation Volume Browser Additional data Links

EMD-7347

CRISPR RNA-guided surveillance complex, pre-nicking

EMD-7347

Single-particle
3.66 Å
EMD-7347 Deposition: 17/01/2018
Map released: 27/06/2018
Last modified: 29/11/2023
Overview 3D View Sample Experiment Validation Volume Browser Additional data Links
Sample Organism: Thermobifida fusca (strain YX), Thermobifida fusca
Sample: CRISPR RNA-guided surveillance complex with Cas3 bound in its pre-nicking state
Fitted models: 6c66 (Avg. Q-score: 0.411)

Deposition Authors: Xiao Y , Luo M
Structure basis for RNA-guided DNA degradation by Cascade and Cas3.
Xiao Y , Luo M , Dolan AE, Liao M , Ke A
(2018) Science , 361
PUBMED: 29880725
DOI: doi:10.1126/science.aat0839
ISSN: 1095-9203
ASTM: SCIEAS
Abstract:
Type I CRISPR-Cas system features a sequential target-searching and degradation process on double-stranded DNA by the RNA-guided Cascade (CRISPR associated complex for antiviral defense) complex and the nuclease-helicase fusion enzyme Cas3, respectively. Here, we present a 3.7-angstrom-resolution cryo-electron microscopy (cryo-EM) structure of the Type I-E Cascade/R-loop/Cas3 complex, poised to initiate DNA degradation. Cas3 distinguishes Cascade conformations and only captures the R-loop-forming Cascade, to avoid cleaving partially complementary targets. Its nuclease domain recruits the nontarget strand (NTS) DNA at a bulged region for the nicking of single-stranded DNA. An additional 4.7-angstrom-resolution cryo-EM structure captures the postnicking state, in which the severed NTS retracts to the helicase entrance, to be threaded for adenosine 5'-triphosphate-dependent processive degradation. These snapshots form the basis for understanding RNA-guided DNA degradation in Type I-E CRISPR-Cas systems.