1w41
|
T.CELER L30E E90A VARIANT
OverviewOverview
The origin of reduced heat capacity change of unfolding (DeltaC(p)), commonly observed in thermophilic proteins is controversial. The, established theory that DeltaC(p) is correlated with change of, solvent-accessible surface area cannot account for the large differences, in DeltaC(p) observed for thermophilic and mesophilic homologous proteins, which are very similar in structures. We have determined the protein, stability curves, which describe the temperature dependency of the free, energy change of unfolding, for a thermophilic ribosomal protein L30e from, Thermococcus celer, and its mesophilic homologue from yeast. Values of, DeltaC(p), obtained by fitting the free energy change of unfolding to the, Gibbs-Helmholtz equation, were 5.3 kJ mol(-1) K(-1) and 10.5 kJ mol(-1), K(-1) for T.celer and yeast L30e, respectively. We have created six, charge-to-neutral mutants of T.celer L30e. Removal of charges at Glu6, Lys9, and Arg92 decreased the melting temperatures of T.celer L30e by, approximately 3-9 degrees C, and the differences in melting temperatures, were smaller with increasing concentration of salt. These results suggest, that these mutations destabilize T.celer L30e by disrupting favorable, electrostatic interactions. To determine whether electrostatic, interactions contribute to the reduced DeltaC(p) of the thermophilic, protein, we have determined DeltaC(p) for wild-type and mutant T.celer, L30e by Gibbs-Helmholtz and by van't Hoff analyses. A concomitant increase, in DeltaC(p) was observed for those charge-to-neutral mutants that, destabilize T.celer L30e by removing favorable electrostatic interactions., The crystal structures of K9A, E90A, and R92A, were determined, and no, structural change was observed. Taken together, our results support the, conclusion that electrostatic interactions contribute to the reduced, DeltaC(p) of T.celer L30e.
About this StructureAbout this Structure
1W41 is a Single protein structure of sequence from Thermococcus celer. Full crystallographic information is available from OCA.
ReferenceReference
Electrostatic interactions contribute to reduced heat capacity change of unfolding in a thermophilic ribosomal protein l30e., Lee CF, Allen MD, Bycroft M, Wong KB, J Mol Biol. 2005 Apr 29;348(2):419-31. PMID:15811378
Page seeded by OCA on Wed Nov 21 05:13:19 2007