1z3l
X-Ray Crystal Structure of a Mutant Ribonuclease S (F8Anb)
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OverviewOverview
While the hydrophobic driving force is thought to be a major contributor to protein stability, it is difficult to experimentally dissect out its contribution to the overall free energy of folding. We have made large to small substitutions of buried hydrophobic residues at positions 8 and 13 in the peptide/protein complex, RNase-S, and have characterized the structures by X-ray crystallography. The thermodynamics of association of these mutant S peptides with S protein was measured in the presence of different concentrations of methanol and ethanol. The reduction in the strength of the hydrophobic driving force in the presence of these organic solvents was estimated from surface-tension data as well as from the dependence of the DeltaC(p) of protein/peptide binding on the alcohol concentration. The data indicated a decrease in the strength of the hydrophobic driving force of about 30-40% over a 0-30% range of the alcohol concentration. We observe that large to small substitutions destabilize the protein. However, the amount of destabilization, relative to the wild type, is independent of the alcohol concentration over the range of alcohol concentrations studied. The data clearly indicate that decreased stability of the mutants is primarily due to the loss of packing interactions rather than a reduced hydrophobic driving force and suggest a value of the hydrophobic driving force of less than 18 cal mol(-)(1) A(2).
About this StructureAbout this Structure
1Z3L is a Protein complex structure of sequences from Bos taurus with as ligand. Active as Pancreatic ribonuclease, with EC number 3.1.27.5 Full crystallographic information is available from OCA.
ReferenceReference
Attempts to delineate the relative contributions of changes in hydrophobicity and packing to changes in stability of ribonuclease S mutants., Das M, Rao BV, Ghosh S, Varadarajan R, Biochemistry. 2005 Apr 19;44(15):5923-30. PMID:15823052
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