Figure 1. Contraction of the active site of substrate-free CYP101 (yellow, 2LQD) compared to camphor-bound CYP101 (green, 2L8M).

The side chains of Phe 87 (B-B′ loop) and Leu 244 and Val 247 on the I helix move to partially occupy the vacancy left by the removal of camphor (cyan spheres). As a result of these displacements, the I helix “kink” is less pronounced in the absence of substrate (see text and Video 1).