1 research outputs found
NMR and Computation Reveal a Pressure-Sensitive Folded Conformation of Trp-Cage
Beyond
defining the structure and stability of folded states of
proteins, primary amino acid sequences determine all of the features
of their conformational landscapes. Characterizing how sequence modulates
the population of protein excited states or folding pathways requires
atomic level detailed structural and energetic information. Such insight
is essential for improving protein design strategies, as well as for
interpreting protein evolution. Here, high pressure NMR and molecular
dynamics simulations were combined to probe the conformational landscape
of a small model protein, the tryptophan cage variant, Tc5b. Pressure
effects on protein conformation are based on volume differences between
states, providing a subtle continuous variable for perturbing conformations.
2D proton TOCSY spectra of Tc5b were acquired as a function of pressure
at different temperature, pH, and urea concentration. In contrast
to urea and pH which lead to unfolding of Tc5b, pressure resulted
in modulation of the structures that are populated within the folded
state basin. The results of molecular dynamics simulations on Tc5b
displayed remarkable agreement with the NMR data. Principal component
analysis identified two structural subensembles in the folded state
basin, one of which was strongly destabilized by pressure. The pressure-dependent
structural perturbations observed by NMR coincided precisely with
the changes in secondary structure associated with the shifting populations
in the folded state basin observed in the simulations. These results
highlight the deep structural insight afforded by pressure perturbation
in conjunction with high resolution experimental and advanced computational
tools