The effects of eight mutations on the thermodynamics of the reversible thermal unfolding of staphylococcal nuclease have been determined over a range of pH and protein concentration by means of differential scanning calorimetry. Variation of the protein concentration was included in our study because we found a significant dependence of the thermodynamics of protein unfolding on concentration. Values for the change in the standard free energy of unfolding, delta delta G0d, produced by the mutations in the pH range 5.0-7.0 varied from 1.9 kcal mol-1 (apparent stabilization) for H124L to -2.8 kcal mol-1 (apparent destabilization) for L25A. As has been observed in numerous other cases, there is no correlation in magnitude or sign between delta delta G0d and the corresponding values for delta delta Hd and T delta delta S0d, the latter quantities being in most cases much larger in magnitude than delta delta G0d. This fact emphasizes the difficulty in attempting to correlate the thermodynamic changes with structural changes observed by X-ray crystallography. Study holds ProTherm entries: 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 2156, 2157, 2158, 2159, 13187, 13188, 13189, 13190, 13191, 13192, 13193, 13194, 13195, 13196, 13197, 13198, 13946, 13947, 13948, 13949 Extra Details: thermal unfolding; free energies of unfolding; differential scanning,calorimetry; staphylococcal nuclease
Submitter: Connie Wang
Submission Date: April 24, 2018, 8:14 p.m.
|Number of data points||106|
|Proteins||Thermonuclease ; Thermonuclease|
|Assays/Quantities/Protocols||Experimental Assay: dCp temp:47.0 C ; Experimental Assay: ddG temp:47.0 C ; Experimental Assay: dCp pH:5.0, temp:47.0 C ; Experimental Assay: ddG pH:5.0, temp:47.0 C ; Experimental Assay: dCp temp:51.4 C ; Experimental Assay: ddG temp:51.4 C ; Experimental Assay: dHcal pH:5.0 ; Experimental Assay: Tm pH:5.0 ; Experimental Assay: dHvH pH:5.0 ; Experimental Assay: dCp pH:5.0 ; Experimental Assay: dHcal pH:7.0 ; Experimental Assay: Tm pH:7.0 ; Experimental Assay: dHvH pH:7.0 ; Experimental Assay: dCp ; Derived Quantity: dTm pH:5.0 ; Derived Quantity: dTm pH:7.0|
|Libraries||Mutations for sequence ATSTKKLHKEPATLIKAIDGDTVKLMYKGQPMTFRLLLVDTPETKHPKKGVEKYGPEASAFTKKMVENAKKIEVEFDKGQRTDKYGRGLAYIYADGKMVNEALVRQGLAKVAYVYKPNNTHEQHLRKSEAQAKKEKLNIWSEDNADSGQ|