Here you can see a cryoEM structure of the Rep68-AAVS1 heptameric complex of the AAV-2 adenovirus (PDB code: 9BC5)

Rendering by Francisco J. Enguita made with #ProteinImager

3dproteinimaging.com/protein-imag...

#SciArt #molecularart #adenovirus #complex #DNA #integrase #cryoem

We propose a hypothetical spacer acquisition mechanism in type II-A CRISPR-Cas systems, consisting of prespacer selection by the Cas9-Cas1-Cas2-Csn2 supercomplex, and its step-wise hand-off to a Cas1-Cas2 #integrase.

We have determined the #cryoEM structure of the Csn2 - #integrase subcomplex forming the Interface 4. Interface 4 mutations abolished acquisition of new spacers in the native S. thermophilus host.

The catalytically inactive supercomplex may employ the alternative Cas1-Csn2 interface (Interface 4) to recruit the catalytic Cas1-Cas2 #integrase, or capture the mobile part of the Cas1-Cas2 #integrase that makes part of the supercomplex.

Here, we present #cryoEM structures of the type II-A prespacer selection supercomplex consisting of #Cas9 RNP, Cas1-Cas2 #integrase fragment and Csn2 ring in the DNA-scanning and two different PAM-bound configurations.

In type II-A #CRISPR-Cas systems acquisition of new spacers involves the effector nuclease #Cas9, which forms a ‘supercomplex’ with the Cas1-Cas2 #integrase and the ring-shaped Csn2 protein. The supercomplex structure and the role of Csn2 remain unknown.