PT  - JOURNAL ARTICLE
AU  - Pengfei Tian
AU  - Annette Steward
AU  - Renuka Kudva
AU  - Ting Su
AU  - Patrick J. Shilling
AU  - Adrian A. Nickson
AU  - Jeffrey J. Hollins
AU  - Roland Beckmann
AU  - Gunnar Von Heijne
AU  - Robert B. Best
AU  - Jane Clarke
TI  - The Folding Pathway of an Ig Domain is Conserved On and Off the Ribosome
AID  - 10.1101/253013
DP  - 2018 Jan 01
TA  - bioRxiv
PG  - 253013
4099  - http://biorxiv.org/content/early/2018/01/24/253013.short
4100  - http://biorxiv.org/content/early/2018/01/24/253013.full
AB  - Proteins that fold cotranslationally do so in a restricted configurational space, due to the volume occupied by the ribosome. Here, we investigate the cotranslational folding of an all-β immunoglobulin domain, titin I27, whose intrinsic folding mechanism has been extensively characterized. Using an arrest peptide-based assay and structural studies by cryo-EM, we show that I27 folds in the mouth of the ribosome exit tunnel. Simulations that use a kinetic model for the force-dependence of escape from arrest, accurately predict the fraction of folded protein as a function of length. We used these simulations to probe the folding pathway on and off the ribosome. Our simulations - which also reproduce experiments on mutant forms of I27 - show that I27 folds, while still sequestered in the ribosome, by essentially the same pathway as free I27, with only subtle shifts of critical contacts from the C to the N terminus.