FIGURE 6.

Stabilization of the CASQ dimer by the formation of a H-bond network. A, intermolecular surface of the dimer. The structure of the front-to-front dimer between chains A and B is stabilized through intermolecular H-bonding by loop-helix interactions of Asp³² with Lys⁶⁸ and Lys⁶⁴ (red ellipse) and helix-helix interactions of Lys⁶⁸ with Glu⁷⁴ and Glu⁷⁸ (black triangle). The surface of chain A is shown in pink, and that of chain B is shown in blue. The interacting surface has overlapping pink and blue colors. B, the H-bond network formed by the DGKDR ring system in a dimer. Black dashes represent H-bonds. The conformational flip of Lys³¹-Asp³² brings together helices from chains A (in red) and B (in green) into proximity and is stabilized by the H-bond network.