Science 13Mar2020

proteomics and native mass spectrometry experiments and C.V.R.
supervised the mass spectrometry. J.L.R. and Y.M.A. wrote the
manuscript and prepared the figures with input from the other
authors.Competing interests:The authors declare no competing
interests.Data and materials availability:Cryo-EM maps are
deposited in the Electron Microscopy Data Bank under accession
numbers EMD-21317 to 21319 for maps of the intact complex and
21345 to 213453 for maps from focused refinement. Atomic models
are deposited in the Protein Data Bank under accession numbers

6VQ6, 6VQ7, and 6VQ8 for composite models and 6VQ9, 6VQA,

6VQB, 6VQC, 6VQG, 6VQH, 6VQI, 6VQJ, and 6VQK for models built

into maps from focused refinement. The SidK-3×FLAG expression

vector is available from J.L.R.

SUPPLEMENTARY MATERIALS

science.sciencemag.org/content/367/6483/1240/suppl/DC1

Materials and Methods

Figs. S1 to S14

Tables S1 to S6

References ( 57 – 78 )

Movie S1

View/request a protocol for this paper fromBio-protocol.

28 August 2019; accepted 12 February 2020

10.1126/science.aaz2924

Abbaset al.,Science 367 , 1240–1246 (2020) 13 March 2020 7of7

RESEARCH | REPORT