Fig. 5: NTR controls the conformational selection of the structured La-module in LARP6.
From: An intrinsically disordered region mediates RNA-binding selectivity and cellular activities of LARP6
a Far-UV CD spectra of recombinant LARP6 NTD, La-module, and NTR protein segments. b Zoom-in of the overlay of 1H-15N TROSY NMR spectra of recombinant LARP6 NTD and NTR, in the window of 1H-resonances for flexible/unstructured tails. Several peaks undergo CSP (grey arrows) upon NTR tethering to the structured La-module. Full spectra are reported in Supplementary Fig. 5a. c Overlay of 1H-15N TROSY NMR spectra of recombinant LARP6 La-module and NTD. The inset at the top-left corner shows a zoomed-in view in a region where several perturbations of the La-module peaks are observed upon the tethering of the NTR (grey arrows). d Analysis of NTR resonances in the context of the NTD. Top: CSP of the residues of the NTR in the context of the NTD. Bottom: R2 NMR backbone relaxation of the residues of the NTR in isolation (green) vs. in the context of the NTD (black). Relaxation rates were determined from exponential least-squares fitting of peak volumes. Error bars indicate mean ± SD, estimated from n = 100 cycles of Monte Carlo simulation and refitting. Three approximate segments exhibiting larger CSPs and enhanced R2 are highlighted: S1 = residues 25–43; S2 = residues 45–58; S3 = residues 77–83. e Overlay of the normalised Kratky plots obtained from the SEC-SAXS data analysis of recombinant LARP6 NTD, La-module, and NTR. The NTR in isolation shows high data points deviation from the typical globular proteins (I(q)/I(0)×(qRg)2 = 1.104, qRg = 1.73—indicated by the grey dotted cross), plateau at high qRg, and large data scattering. The La-module and the NTD exhibit a maximum slightly above the typical value for globular proteins, and slow data points decay, indicative of elongated conformations. The scattering of the NTD datapoints is lower than the La-module, suggestive of specific La-module conformations selection by NTR. Full data sets are reported in Supplementary Fig. 5e–g. f Overlay of the P(r) distance distribution functions of recombinant LARP6 NTD, La-module, and NTR. The NTR exhibits multiple states, some of which are highly extended. The La-module shows two main conformations, whilst The NTD exhibits a single state.
