Figure 4.

Schematic representation of the change in the unit cell in SEPT9GC complexes. GDP-bound crystals of SEPT9GC have the blue monoclinic cell with filaments running in the direction of the cell diagonal [101]. On soaking these crystals with excess GTPγS there is a unit-cell change leading to a new monoclinic cell of approximately twice the volume in which the filaments run along the a direction [100]. The red cell is the predicted new cell, based on the original blue cell. The c parameter is well predicted but a is foreshortened in accordance with the corresponding shrinkage of the filament which occurs on substituting GDP for GTPγS.