Figure 6. G-strand unfurling may occur upon hexamer formation.

¹⁵N CPMG relaxation dispersion data at 750 MHz (magenta) and 950 MHz (red) (180 μM ΔN6, pH 6.2 (26% ΔN6 molecules are monomers, 48% are in dimers, 26% are in hexamers) for residues (a) 51, (b) 37, (c) 89, and (d) 92. Residues 37 and 51 report on intermolecular interactions that describe dimer and/or hexamer formation (schematic, top left), while residues 89 and 92 do not lie in an interface and report instead in the dynamics of the G strand in the different assemblies formed. The position of all five residues used in the cluster analysis of G strand dynamics is shown in spheres on the structure of ΔN6 (blue cartoon, top right). Pro32 is shown as a magenta sphere. Solid lines represent global fits to the Bloch-McConnell equations (Materials and methods) for each cluster of residues. The extracted parameters of the global fit for the two processes (k_ex^bind and k_ex^G) are indicated above the plots.

Figure 6—figure supplement 1. Hexamer formation increases the dynamics of the G strand.

(a) Location of the G strand in relation to the dimer and hexamer interfaces. Dimer one in the hexamer is shown in a cartoon representation while dimers 2 and 3 are shown as semi-transparent surfaces. The positions of the amide protons for residues 87, 89, 91, 92 are shown as gray spheres and the residues that take part in both the dimer and hexamer interfaces are shown as red spheres on the structure of dimer 1. A schematic of the assembly is shown alongside. ¹⁵N relaxation dispersion CPMG data for residues (b) 87, (c) 89, (d) 91 and (e) 92 at 950 MHz (red) and 750 MHz (magenta) of 180 μM ΔN6, pH 6.2. Solid lines represent the global fits to all residues in the cluster to the slow exchange model which yields a k_ex^G of 205 ± 150 s⁻¹. CPMG data for the same residues (f) 87, (g) 89, (h) 91 and (i) 92 at 750 MHz (blue) and 600 MHz (gray) using 480 μM ΔN6. Solid lines represent global fits to the fast exchange model which yields a k_ex^G of 1170 ± 196 s⁻¹.