A thermodynamic study of mutant forms of Streptomyces subtilisin inhibitor. III. Replacements of a hyper-exposed residue, Met73.


Abstract

Amino acid replacements of Met73, which is hyper-exposed in the native structure, with Asp, Glu, Lys, Gly, Ala, Val, Leu or Ile changed the stability of Streptomyces subtilism inhibitor by +1.60 to -0.94 kcal/mol-1 in free energy at 82.21 degrees C at pH 7.0, with higher hydrophobicity of the replacing amino acid side-chain showing a correlation with lower stability. Thermodynamic parameters obtained from detailed calorimetric analyses gave a nearly proportional relation between the entropy change and the enthalpy change of denaturation, i.e. T delta delta S degrees = -0.03 (+/- 0.11) + 1.14 (+/- 0.03) delta delta H, with the linear correlation coefficient 0.996 for 18 data points. This proportionality observed uniquely for the substitutions at position 73 was caused primarily by the water/side-chain interaction, or hydration effect, which can account for the majority of the changes in enthalpy and entropy induced by the mutations. Study holds ProTherm entries: 3066, 3067, 3068, 3069, 3070, 3071, 3072, 3073, 3074, 3075, 3076, 3077, 3078, 3079, 3080, 3081, 3082, 3083, 3084, 3085, 3086, 3087, 3088, 3089, 14127, 14128, 14129, 14130, 14131, 14132, 14133, 14134, 14135, 14136, 14137, 14138, 14139, 14140, 14141, 14142, 14143, 14144, 14145, 14146, 14147, 14148, 14149, 14150 Extra Details: ddG was computed at Tm of wild type calorimetry; protein stability; hydrophobicity;,hydration; mutagenesis

Submission Details

ID: iGu9ym3

Submitter: Connie Wang

Submission Date: April 24, 2018, 8:21 p.m.

Version: 1

Publication Details
Tamura A;Sturtevant JM,J. Mol. Biol. (1995) A thermodynamic study of mutant forms of Streptomyces subtilisin inhibitor. III. Replacements of a hyper-exposed residue, Met73. PMID:7783217
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