Nmrfam sparky

All NMR experiments were performed on a Bruker Bruker Avance III 700 MHz spectrometer, except for the 3D assignment of β2AR-Cter performed on a 800 MHz, and for the ³J_HNHA of GHSR-Cter performed on a 500 MHz. The 700 MHz and 800 MHz spectrometers are equipped with a cryogenic triple-resonance (¹H, ¹⁵N, ¹³C) probe and shielded z-gradients. All NMR experiments were recorded at 20 °C in a buffer (named NMR buffer) composed of 50 mM Bis-Tris pH 6.7, 150 mM NaCl, 1 mM EDTA, 0.5 mM TCEP, 5% D₂O (Eurisotop), and 5 mM DSS-d6 (2,2-dimethyl-2-silapentane-5-sulfonate, Sigma) as internal reference [42 ]. All experiments used the pulse sequences provided by Bruker TOPSPIN 3.2. Squared cosine apodization was used in indirect dimensions, prior to zero-filling and Fourier transformation using TOPSPIN (version 4.0.6, Bruker) and data processing was performed using NMRFAM-SPARKY (version 1.414, [43 (link)]). For each NMR experiments, concentrations of GPCR-Cters were indicated in Table S1. For all NMR experiments, data were measured for all residues of C-terminus regions excepted proline residues, the residue A339 of β2AR-Cter, and the first N-terminal residue.

¹H-¹⁵N heterogenous single-quantum coherence (HSQC) NMR measurements were performed using 100 µM ¹⁵N-labeled ɑSyn dissolved in fibrillation buffer prepared in H₂O/D₂O (9:1, v/v). The ¹⁵N-labeled ɑSyn was expressed in M9 minimal medium containing ¹⁵NH₄Cl and purified as described for the unlabeled protein. NMR spectra were acquired at 37 °C on a Bruker AVANCE III HD 600 MHz NMR spectrometer equipped with a 5 mm quadruple resonance cryogenic probe (Bruker Biospin). The data size and spectral width were 256 (t1) × 2048 (t2) and 1338 Hz (ω1, ¹⁵N) × 9,615 Hz (ω2, ¹H), respectively. The carrier frequencies of ¹H and ¹⁵N were 4.7 and 118 ppm, respectively. The number of scans/FID was 32. The repetition time was 1 s. The peak assignment at pH 7.4 was achieved employing the assignment data reported by El Turk et al. [61 (link)]. The chemical shift perturbation (CSP) is calculated as follows: $$\mathrm{\Delta }\delta =\sqrt{{\mathrm{\Delta }\delta }_{\mathrm{H}}^2+{\left(\frac{1}{8},{\mathrm{\Delta }\delta }_{\mathrm{N}}\right)}^2},$$ where Δδ_H and Δδ_N are the chemical shift changes (in ppm) with respect to the H and N axes, respectively. All NMR spectra were processed with Topspin (Bruker Biospin), NMRPipe [15 (link)] and NMRFAM-sparky [30 (link)].