Fig. 3: Nascent chains bind the apical domains and C-terminal tails of GroEL.
From: GroEL/ES chaperonin unfolds then encapsulates a nascent protein on the ribosome
a Hydrogen/deuterium exchange-mass spectrometry (HDX-MS) experiment. b Protection of GroEL induced by RNC binding. Difference in deuterium uptake after 100 s, between GroEL bound to RNC1-510mut and isolated GroEL. Values are plotted for individual GroEL peptides. Negative values indicate less deuteration of a peptide in RNC-bound GroEL relative to isolated GroEL, and sites with a difference in deuterium uptake >0.5 Da are coloured blue. Data are presented as mean ± SD, n = 3 independent labelling reactions. c Sites of RNC1-510mut-induced protection from deuterium exchange, mapped onto the domain organisation and predicted structure of monomeric GroEL (AF-P0A6F5-F1). Crosslink sites to NC1-510mut are indicated on the domain schematic with orange asterisks. d As in (c), shown on a top-view tetradecameric GroEL. The C-tails protrude into the central cavity. e As in (c), showing a side-view of tetradecameric GroEL (PDB: 5W0S84). Left, outer surface. Right, inner surface. GroEL residues that crosslinked to NC1-510mut are shown in orange. Sites with a difference in deuterium uptake >0.5 Da are coloured blue. f Visualisation of GroEL:RNC assemblies. Left: Negative stain electron microscopy (nsEM) micrograph of DSBU-crosslinked GroEL:RNC1-510mut assemblies. 500 independent micrographs were collected. The scale bar corresponds to 100 nm. Examples of GroEL molecules positioned near ribosomes are circled (1–4). Right: 2D class averages of GroEL and 70S ribosomes. g NC density spans the GroEL cavity at the apical domains. 3D reconstruction of DSBU-crosslinked GroEL:RNC1-510mut (map iv) from nsEM, viewed from the top and side. The structure of GroEL (PDB: 5W0S84) is docked into the map, and extra density corresponding to the NC is coloured black. Source data are provided in Supplementary Data 1.
