jp6b02166_si_001.pdf (1.12 MB)
Coupling Protein Dynamics with Proton Transport in Human Carbonic Anhydrase II
journal contribution
posted on 2016-04-09, 00:00 authored by Srabani Taraphder, C. Mark Maupin, Jessica
M. J. Swanson, Gregory A. VothThe
role of protein dynamics in enzyme catalysis is one of the
most highly debated topics in enzymology. The main controversy centers
around what may be defined as functionally significant conformational
fluctuations and how, if at all, these fluctuations couple to enzyme
catalyzed events. To shed light on this debate, the conformational
dynamics along the transition path surmounting the highest free energy
barrier have been herein investigated for the rate limiting proton
transport event in human carbonic anhydrase (HCA) II. Special attention
has been placed on whether the motion of an excess proton is correlated
with fluctuations in the surrounding protein and solvent matrix, which
may be rare on the picosecond and subpicosecond time scales of molecular
motions. It is found that several active site residues, which do not
directly participate in the proton transport event, have a significant
impact on the dynamics of the excess proton. These secondary participants
are shown to strongly influence the active site environment, resulting
in the creation of water clusters that are conducive to fast, moderately
slow, or slow proton transport events. The identification and characterization
of these secondary participants illuminates the role of protein dynamics
in the catalytic efficiency of HCA II.