Accessing Structure, Dynamics and Function of Biological Macromolecules by NMR Through Advances in Isotope Labeling

Abstract

NMR spectroscopy has become an indispensable tool for
high-resolution structure determination of biomolecules at physiological
conditions both in solutions and solids. Currently, NMR is routinely used
to study the structure and dynamics of high molecular weight biomolecules
in sizes ranging up to ~ 50–100 kDa and to evaluate complexes
as large as 500–1 MDa. The latest advances in spectrometer technology,
methodologies and advents in newer and highly innovative NMR
active isotope-labeling strategies now enable us to overcome an earlier
speculated size barrier of ~ 20 kDa for de novo structure determination.
Of these, developments in NMR active isotope-labeling strategies are of
great significance as they allow reduction in spectral crowding and yield
selective spin correlations. Moreover, NMR isotope enrichment schemes
permit exploitation of heteronuclear magnetization transfer pathways
for enhanced sensitivity and selectivity. Functionally relevant sites or
domains in very large complexes can also be selectively evaluated by
specific labeling strategies in which other regions are masked. Further,
labeling schemes can be effectively used to favourably overcome deleterious
relaxation effects. Recently evolved labeling strategies include
uniform labeling, perdeuteration, specific labeling of an amino acid or a
side chain, selective deuteration or protonation, segmental labeling and
biosynthesis of biomolecules in various organisms, cell lines and cellfree
systems. The present review is aimed at introducing various NMR
isotope labeling strategies and discusses their impact in widening the
scope of biomolecular NMR spectroscopy driven structural biology.