2018-07-18 REL RCSB RCSB RCSB 2017-01-13 2017-02-08 2017-04-26 2018-07-18 Chowdhury S Lander GC Rollins MF Carter J Golden MS Wilkinson RA Bondy-Denomy J Wiedenheft B Rollins MF Chowdhury S Carter J Golden SM Wilkinson RA Bondy-Denomy J Lander GC Wiedenheft B Proc. Natl. Acad. Sci. U.S.A. US 114 E5113 E5121 2017 28438998 doi:10.1073/pnas.1616395114 1091-6490 0040 PNASA6 EMD-8558 associated EM volume Complex containing dimer of Cas2/3 protein and tetramer of Cas1 protein. Complex containing dimer of Cas2/3 protein and tetramer of Cas1 protein. 0 Pseudomonas aeruginosa PA14 Escherichia coli BL21(DE3) 0.386 singleParticle particle 0.03 7.5

20 mM HEPES, 150 mM KCl

NEGATIVE Uranyl Formate

Sample absorbed on carbon surface was stained with 2% (w/v) Uranyl Formate solution, and finally air-dried after blotting off excess stain.

400 mesh Cu-Rh maxtaform grids (Electron Microscopy Sciences) that were coated with a thin layer of amorphous carbon. COPPER/RHODIUM 400 CARBON CONTINUOUS GLOW DISCHARGE AIR 0.02

15mA current

Mono dispersed protein solution

FEI TECNAI SPIRIT FLOOD BEAM BRIGHT FIELD LAB6 120 100.0 2.7 1.0 0.99 1.0 0.99 52000. SIDE ENTRY, EUCENTRIC NITROGEN 293.0 295.0 TVIPS TEMCAM-F416 (4k x 4k) 4096 4096 15.6 1 1159 0.479 30.0 1

Automated image acquisition software Leginon was used for data collection.

221700

Difference of Gaussian (DoG)-based automated particle picker, implemented in Appion processing package was used for particle selection.

CTFFIND4

Ctffind4 was used for determining the CTF of each micrograph. Phases of each micrographs were flipped before particle extraction.

An initial 3D reference was generated with selected 2D class averages using sxviper program of the SPARX EM data processing package (sparx-em.org)

1 C1 FOURIER SPACE 15.6 FSC 0.143 CUT-OFF RELION 1.4 26403 PROJECTION MATCHING RELION 1.4 PROJECTION MATCHING RELION 1.4 8 RELION 1.4