Fig. 5. Schematic pictures of the first normal mode.

(A) Three parts (marked as green, yellow, and pink) in the protein rotate against each other (shown by the colored arrows). The region marked red is the catalytic site. The entrance of the substrate access channel formed by the B′ helices and F/G loops is marked brown. (B) Cross-sectional view schematically illustrating the opening of the substrate access channel step by step via mode 1. The black arrow points to the entrance of the channel.