Exploring the entire conformational space of proteins by high-pressure
NMR
K. Akasaka
Department of Biotechnological Science, School of
Biology-Oriented Science and Technology, Kinki University, Wakayama
649-6493, Japan and Cellular Signaling Laboratory, RIKEN Harima Institute,
Hyogo 679-5148, Japan
Abstract: A protein in solution is a thermodynamic entity, spanning,
in principle, the entire allowed conformational space from the fully
folded N to the fully unfolded U. Although some alternately or partially
folded higher-energy conformers may coexist with N and U, they are seldom
detected spectroscopically because their populations are usually quite
low under physiological conditions. I describe here a new type of experiment,
a combination of multidimensional NMR spectroscopy with pressure, that
is capable of detecting and analyzing structures and thermodynamic stability
of these higher-energy conformers. The idea is based on the finding
that under physiological conditions the conformational order of a globular
protein normally decreases in parallel with its partial molar volume
(negative dV), so that under equilibrium
conditions, the population is shifted to a less and-less-ordered conformer
with increasing pressure. In principle, with the high space resolution
of the multidimensional NMR, the method enables one to explore protein
structure and stability in atomic detail in a wide conformational space
from N to U with pressure and temperature as variables. The method will
provide us with a strong basis for understanding the fundamental phenomena
of proteins:function, folding, and aggregation.
*Plenary lecture presented at the 17th IUPAC Conference
on Chemical Thermodynamics (ICCT), Rostock, Germany, 28 July - 2 August
2002. Other presentations are published in this issue,
pp.859 -936.
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