Journal Title
Title of Journal: J Biomol NMR
|
Abbravation: Journal of Biomolecular NMR
|
Publisher
Springer Netherlands
|
|
|
|
Authors: Jun Xu Yi Xue Nikolai R Skrynnikov
Publish Date: 2009/07/07
Volume: 45, Issue: 1-2, Pages: 57-72
Abstract
In solution the correlation time of the overall protein tumbling τ R plays a role of a natural dynamics cutoff—internal motions with correlation times on the order of τ R or longer cannot be reliably identified on the basis of spin relaxation data It has been proposed some time ago that the ‘observation window’ of solution experiments can be expanded by changing the viscosity of solvent to raise the value of τ R To further explore this concept we prepared a series of samples of αspectrin SH3 domain in solvent with increasing concentration of glycerol In addition to the conventional 15N labeling the protein was labeled in the Val Leu methyl positions 13CHD2 on a deuterated background The collected relaxation data were used in asymmetric fashion backbone 15N relaxation rates were used to determine τ R across the series of samples while methyl 13C data were used to probe local dynamics sidechain motions In interpreting the results it has been initially suggested that addition of glycerol leads only to increases in τ R whereas local motional parameters remain unchanged Thus the data from multiple samples can be analyzed jointly with τ R playing the role of experimentally controlled variable Based on this concept the extended modelfree model was constructed with the intent to capture the effect of ns timescale rotameric jumps in valine and leucine side chains Using this model we made a positive identification of nanosecond dynamics in Val23 where ns motions were already observed earlier In several other cases however only tentative identification was possible The lack of definitive results was due to the approximate character of the model—contrary to what has been assumed addition of glycerol led to a gradual ‘stiffening’ of the protein This and other observations also shed light on the interaction of the protein with glycerol which is one of the naturally occurring osmoprotectants In particular it has been found that the overall protein tumbling is controlled by the bulk solvent and not by a thin solvation layer which contains a higher proportion of water
Keywords:
.
|
Other Papers In This Journal:
|