Biomedical Engineering Reference
In-Depth Information
CHAPTER 7
NMR Relaxation Dispersion
Studies of Large Enzymes in
Solution
SEAN K. WHITTIER a
AND J. PATRICK LORIA* a,b
a Department of Molecular Biophysics and Biochemistry; b Department of
Chemistry, Yale University, New Haven, CT 06511, USA
*E-mail: patrick.loria@yale.edu
7.1 Introduction
Intramolecular motions play an important role in protein function. These
motions are both spatially and temporally diverse, ranging from smaller
amplitude, picosecond side-chain fluctuations to larger amplitude, low-
frequency motions occurring over a timescale of up to many seconds.
Although motions occurring at any timescale in this span may be functionally
significant, those in the microsecond to millisecond (ms-ms) range are
particularly important for enzyme function 2-6 and are the focus of this
chapter. These motions, which include such processes as active-site loop
closure 2,7
and domain rearrangement, 8
can be involved in ligand binding, 9,10
product release, 11,12
or allostery, 13,14
and may additionally constitute the rate-
limiting step in catalysis. 4,15,16
An encompassing view of enzyme function,
therefore,
requires
careful
characterisation
of
motions
occurring
on
this
timescale.
There are currently a variety of experimental spectroscopic techniques
available to probe ms-ms protein dynamics, including EPR, 17
fluorescence, 18
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