Fig. 1. Site-specifically ¹⁹F-labelled RNCs report on the folding of FLN5 on and off the ribosome.

a, Schematic of production of ¹⁹F-labelled RNCs (Methods). CmR, cloramphenicol resistance gene; araBAD, l-arabinose operon; ampR, ampicillin resistance gene; T7lac, T7 promoter inducible by isopropyl ß-d-1-thiogalactopyranoside (IPTG). b, The ¹⁹F NMR spectra of a RNC with a cleavable FLN5 domain, before and after addition of tobacco etch virus (TEV) protease and purification of component parts (Extended Data Fig. 1). c, The ¹⁹F NMR spectra of isolated FLN5 and FLN5 + 110 RNC, and isolated FLN5 Y719E and FLN5 + 21 RNC. Observed and fitted spectra are shown in grey and red/blue respectively (298 K, 500 MHz). δ_F, 9F chemical shift. RNC spectra magnified by a factor of ×2. d, The 2D ¹H,¹⁵N NMR (selective optimized flip angle short transient (SOFAST) heteronuclear multiple quantum coherence (HMQC)) spectra of ¹⁵N-labelled and ¹⁵N/¹⁹F-labelled isolated FLN5 and FLN5 Y719E (298 K and 283 K, respectively; 800 MHz). δ_N, ¹⁵N chemical shift; δ_H, ¹H chemical shift. e, Crystal structure of FLN5 (Protein Data Bank (PDB) no. 1QFH) coloured by residue-specific ¹H,¹⁵N amide backbone chemical shift perturbations (CSP) observed following ¹⁹F incorporation at position 655 (Extended Data Fig. 3). The N and C termini are shown.

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