1/ How do proteins take their shape in the cell? Insights from our article with @JackJKelly @TheYueLab @UniofOxford @v_paavilainen @HiLIFE_Helsinki @LHapponen @lunduniversity @structbiolbxl @imperialcollege @pfizer nature.com/articles/s4159… #OpenAccess 🧵👇 
2/ #AlphaFold can predict the folded protein shape, but not the complicated folding process itself. Often cells use protein complexes called chaperonins to help other proteins to fold. Here we purified a chaperonin called TRiC from cultured human cells.
3/ Purification was possible only by using #CRISPR genetic scissors. We introduced a purification handle in one of the 8 TRiC subunits. This allowed purification of the endogenous chaperonin as opposed to an engineered version of it. Quite a TRiCK! #samplerevolution
4/ We then built an atomic model of the chaperonin based on #cryoEM data. By our symmetry relaxation data processing method, we could classify nearly 4 million images into subsets revealing two different client proteins inside TRiC.
5/ To provide further support for our results, we used #MassSpectrometry. This allowed verifying the presence of different protein species in our purified sample as well as cellular protein-protein interactions indicated by the models.
6/ The #cryoEM data and models revealed folding intermediates of both actin and tubulin, the two major proteins making the cell’s cytoskeleton. To our surprise, the folding of actin was seen to be assisted by a helper chaperone (PhLP2A), residing inside of our big chaperonin.
7/ By combining our results with earlier data from others, we could piece together an atomic level mechanistic model of how this nanomachine holds its client proteins in place and engages with them to catalyze their folding.
8/ We are grateful for our funders and partners @SuomenAkatemia @pfizer @instructhub @scilifelab @CSCfi
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