Conformation change process of the two enzymes. Panel
(a) shows
the motion from His186 and its effect on the nicotinamide in the wild-type
pathway 1, on the start (blue, 300 fs prior to the transition state)
and the end (red, the transition state) of the motion, viewing from
the top of the nicotinamide ring. The direction of the His186 motion
is labeled by the red arrow, and the direction of the effect of the
motion is shown by the black arrow. The His186 imidazole ring is labeled
by spheres. The direction of the His186 imidazole ring center-of-mass
movement is shown as the black dashed line. Panel (b) shows the detailed
conformation change of the nicotinamide ring, viewing from the front
direction, at 300 fs prior to the transition state (blue), 100 fs
prior to the transition state (red), and the transition state (yellow).
The NADH ribose ring and Tyr356 are colored gray. The direction of
the movement of the acceptor atom is labeled by the black arrow. Panel
(c) shows the His186 side-chain center-of-mass root-mean-square deviation
(RMSD) using the transition state as a reference, in a 600 fs window
centered at each pathway’s transition state. The black, red,
blue, green, and orange solid lines represent the wild-type pathway
1, the wild-type pathway 2, the N189A mutant pathway 1, the N189A
mutant pathway 2, and the N189A mutant pathway 3, respectively. Panel
(d) shows three structures of N189A pathway 3 taken at 400 fs (colored
blue) and 200 fs prior to the transition state (colored red and yellow).
The NADH classical ribose ring and the Tyr356 residue are colored
in dark gray. The donor atom and the acceptor atom are labeled by
spheres. The direction of the acceptor atom movement is labeled by
the black arrow. The RMSD of the center of mass of the FMN isoalloxazine
middle ring is shown in (e), for the wild-type pathway 1 (black),
the wild-type pathway 2 (red), the N189A mutant pathway 1 (blue),
the N189A mutant pathway 2 (green), and the N189A mutant pathway 3
(yellow), in a 600 fs time window centered at the transition state.
Panel (f) shows the overlay of two structures: 100 fs prior to transition
state of the wild-type MR pathway 1 (blue) and 200 fs prior to the
transition state of the N189A mutant pathway 3 (red). The black and
red arrows represent the relative direction between the wall formed
by Tyr356 and the NADH ribose ring, and the nicotinamide pyridine,
of the wild type and the N189A mutant, respectively.