Fig. 3: GEF-Tu folds through a co-translational intermediate.
a Folding scores obtained from AP Profiling experiments exhibit folding peaks for the partially (around ncodons = 200) and fully (around ncodons = 230) extruded G-domain of EF-Tu (GEF-Tu, black line), indicating the population of a co-translational folding intermediate. The folding score of GEF-G (scaled) is plotted for comparison (gray line). b Folding scores mapped onto the structure of GEF-Tu indicate that the intermediate forms occur when helix 5 is being extruded from the ribosome. c Single-molecule optical tweezers recordings of GEF-Tu nascent chain unfolding show reversible population of an on-pathway intermediate (white arrowhead) before complete unfolding (red arrowhead). d The structural region corresponding to the folding intermediate (red), based on length changes measured in optical tweezers experiments, comprises the N-terminus of GEF-Tu up to helix 5. The unstructured part of the domain in the intermediate is shown as a transparent outline. The corresponding fragment from GEF-G (pink), with identical topology and a very similar structure, is shown for comparison. e Position of the G’ insertion in GEF-G relative to the GEF-Tu folding intermediate. The G’ insertion is shown in pink, with flanking helices (corresponding to h5 and h6 in panel d) shown semi-transparent. f Comparison of GEF-G and GEF-Tu structures. GEF-Tu lacks the G’ subdomain present in GEF-G that engulfs the last alpha-helix in the domain (cyan). pdb codes: 1efc (EF-Tu) and 4v9p (EF-G). Source data are provided as a Source Data file.
