Fig. 6.

Native-state dynamics of L6-NTD probed by NMR spectroscopy and PET-FCS. a NMR H/D exchange experiments. Amide H/D exchange time of L6-NTD (orange) and WT-NTD (blue) plotted versus residue number. Positions of helices and mutations are indicated on top of the panel. b Exchange times imposed on the structure of WT-NTD (PDB ID: 2LPJ) and of L6-NTD (PDB ID: 6QJY). c {¹H},¹⁵N-hetNOE values of WT-NTD (blue) and L6-NTD (orange) backbone amides plotted versus residue number. Lower values indicate higher flexibility. d {¹H},¹⁵N-hetNOE values imposed on the structure of WT-NTD (PDB ID: 2LPJ) and L6-NTD (PDB ID: 6QJY), respectively. e Reporter design for PET-FCS. Top view of the structure of L6-NTD (PDB ID: 6QJY) indicating the position of the AttoOxa11 fluorescence label (red sphere) attached to the N-terminus (G3C). The side chain of the conserved Trp W10 (blue sphere), which quenches fluorescence of AttoOxa11 upon solvent-exposure, is highlighted. Trp is buried in a network of tertiary interactions (side chains shown as sticks). f PET-FCS autocorrelation functions (G(τ)) recorded from WT-NTD and L6-NTD (blue and orange) modified with AttoOxa11 at position G3C. Data of L6-NTD modified with AttoOxa11 at position Q50C served as a control (cyan). Black lines are fits to the data using a model for translational diffusion of a globule containing two single-exponential relaxations. The control sample was described by a model for translational diffusion only. g Time constants of Trp moving out of the core (τ_out, solid bars) and into the core (τ_in, patterned bars) of WT-NTD (blue) and L6-NTD (orange), calculated from PET-FCS data. Error bars are propagated s.e. from regression analysis. The comic at the center of the panel illustrates the conformational change and assigns τ_out and τ_in. The NTD is illustrated as gray ellipsoid. Trp W10 (blue sphere) moves between buried and solvent-exposed positions. Source data are provided as Source Data file