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Mannosylglycerate stabilizes staphylococcal nuclease with restriction of slow β‐sheet motions
Author(s) -
Pais Tiago M.,
Lamosa Pedro,
Matzapetakis Manolis,
Turner David L.,
Santos Helena
Publication year - 2012
Publication title -
protein science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.353
H-Index - 175
eISSN - 1469-896X
pISSN - 0961-8368
DOI - 10.1002/pro.2100
Subject(s) - chemistry , crystallography , denaturation (fissile materials) , side chain , biophysics , protein folding , ionic bonding , protein structure , chemical physics , folding (dsp implementation) , molecular dynamics , biochemistry , computational chemistry , biology , ion , organic chemistry , nuclear chemistry , electrical engineering , engineering , polymer
Mannosylglycerate is a compatible solute typical of thermophilic marine microorganisms that has a remarkable ability to protect proteins from thermal denaturation. This ionic solute appears to be a universal stabilizing agent, but the extent of protection depends on the specific protein examined. To understand how mannosylglycerate confers protection, we have been studying its influence on the internal motions of a hyperstable staphylococcal nuclease (SNase). Previously, we found a correlation between the magnitude of protein stabilization and the restriction of fast backbone motions. We now report the effect of mannosylglycerate on the fast motions of side‐chains and on the slower unfolding motions of the protein. Side‐chain motions were assessed by 13 CH 3 relaxation measurements and model‐free analysis while slower unfolding motions were probed by H/D exchange measurements at increasing concentrations of urea. Side‐chain motions were little affected by the presence of different concentrations of mannosylglycerate or even by the presence of urea (0.25 M ), and show no correlation with changes in the thermodynamic stability of SNase. Native hydrogen exchange experiments showed that, contrary to reports on other stabilizing solutes, mannosylglycerate restricts local motions in addition to the global motions of the protein. The protein unfolding/folding pathway remained undisturbed in the presence of mannosylglycerate but the solute showed a specific effect on the local motions of β‐sheet residues. This work reinforces the link between solute‐induced stabilization and restriction of protein motions at different timescales, and shows that the solute preferentially affects specific structural elements of SNase.