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Publication Abstract from PubMed

Most thermophilic proteins tend to have more salt bridges, and achieve higher thermostability by up-shifting and broadening their protein stability curves. While the stabilizing effect of salt-bridge has been extensively studied, experimental data on how salt-bridge influences protein stability curves are scarce. Here, we used double mutant cycles to determine the temperature-dependency of the pair-wise interaction energy and the contribution of salt-bridges to DeltaC(p) in a thermophilic ribosomal protein L30e. Our results showed that the pair-wise interaction energies for the salt-bridges E6/R92 and E62/K46 were stabilizing and insensitive to temperature changes from 298 to 348 K. On the other hand, the pair-wise interaction energies between the control long-range ion-pair of E90/R92 were negligible. The DeltaC(p) of all single and double mutants were determined by Gibbs-Helmholtz and Kirchhoff analyses. We showed that the two stabilizing salt-bridges contributed to a reduction of DeltaC(p) by 0.8-1.0 kJ mol(1) K(1). Taken together, our results suggest that the extra salt-bridges found in thermophilic proteins enhance the thermostability of proteins by reducing DeltaC(p), leading to the up-shifting and broadening of the protein stability curves.

Stabilizing salt-bridge enhances protein thermostability by reducing the heat capacity change of unfolding.,Chan CH, Yu TH, Wong KB PLoS One. 2011;6(6):e21624. Epub 2011 Jun 24. PMID:21720566^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.