Figure 3. NMR HSQC spectra indicating the PDEγ:tubulin interaction.

The [¹H,¹⁵N]-HSQC spectra were collected on 30 μM ¹⁵N-labeled PDEγ, in the absence (black) or presence of 10 μM tubulin dimer in the buffer containing 10 mM PIPES, 1 mM EGTA, 1 mM Mg²⁺, 90% H₂O/10%D₂O, pH 6.2, including either 1 mM GTP (blue) or 1 mM GDP (red).

A. Overlay of the HSQC spectra of free ¹⁵N-PDEγ (black) and ¹⁵N-PDEγ in the presence of tubulin-GTP (blue). The cross peaks corresponding to the indole group of W70 is denoted as W70^ε. B. Overlay of the HSQC spectra of free ¹⁵N-PDEγ (black) and ¹⁵N-PDEγ in the presence of tubulin-GDP (red). C. Overlay of the HSQC spectra of ¹⁵N-PDEγ+tubulin-GTP (blue) and ¹⁵N-PDEγ+tubulin-GDP (red). D. A diagram of PDEγ interactions with different partners. The PDEγ residues that showed most significant interactions with tubulin-GTP are highlighted in orange. The polycationic region is shown in blue. I86 and I87 are labeled red. The Gαt-interacting (green) and RGS9-interacting (cyan) residues are shown based on the crystal structure including the C-terminal half of the PDEγ molecule [16].