posted on 2023-01-05, 01:06authored byVeniamin Chevelkov, Sascha Lange, Henry Sawczyc, Adam Lange
Protein dynamics are an intrinsically important factor
when considering
a protein’s biological function. Understanding these motions
is often limited through the use of static structure determination
methods, namely, X-ray crystallography and cryo-EM. Molecular simulations
have allowed for the prediction of global and local motions of proteins
from these static structures. Nevertheless, determining local dynamics
at residue-specific resolution through direct measurement remains
crucial. Solid-state nuclear magnetic resonance (NMR) is a powerful
tool for studying dynamics in rigid or membrane-bound biomolecules
without prior structural knowledge with the help of relaxation parameters
such as T1 and T1ρ. However, these provide only a combined result of
amplitude and correlation times in the nanosecond–millisecond
frequency range. Thus, direct and independent determination of the
amplitude of motions might considerably improve the accuracy of dynamics
studies. In an ideal situation, the use of cross-polarization would
be the optimal method for measuring the dipolar couplings between
chemically bound heterologous nuclei. This would unambiguously provide
the amplitude of motion per residue. In practice, however, the inhomogeneity
of the applied radio-frequency fields across the sample leads to significant
errors. Here, we present a novel method to eliminate this issue through
including the radio-frequency distribution map in the analysis. This
allows for direct and accurate measurement of residue-specific amplitudes
of motion. Our approach has been applied to the cytoskeletal protein
BacA in filamentous form, as well as to the intramembrane protease
GlpG in lipid bilayers.