An Introduction to Biomolecular Graphics
Figure 3
An overlay of five simvastatin synthetase crystal structures, illustrating varying degrees of hinge closure imparted by ligand binding.
Hinge motion in this two-domain enzyme (PDB 3HLB, 3HLC, 3HLE, 3HLF, and 3HLG) is highlighted by superimposing only atoms in one of the domains (colored grey in this figure). The range of motion is highlighted by the rainbow colors assigned to the upper domain. The orientation of the molecule is chosen to make the range of motion evident (hinge axis normal to the plane of the page). Each of the structures is labeled explicitly in the figure, rather than burying the information in the figure legend. Color coding the labels makes it easier to comprehend how each ligand affects the hinge motion. The structures are represented as Cα traces rather than cartoon ribbons because the motion is relatively small, and the Cα trace allows a more exact representation of the position of the atoms.