To elucidate the role of individual amino acid residues in stabilizing the conformation of a protein, we have constructed a series of variant alpha subunits of tryptophan synthase from Escherichia coli substituted by each of 20 amino acids at position 49, which is buried in the interior of the protein. The stabilities were quantitatively examined except for the mutant protein substituted by arginine, which was not obtained in enough quantity. The Gibbs energy of unfolding in water and the activation Gibbs energy of unfolding in 3 M guanidine hydrochloride for each protein were compared at pH 7.0 and pH 9.0. The Gibbs energy of unfolding in water at pH 7.0 varied from 0.72 to 1.92 times that of the wild-type protein by the substitutions, but the activation Gibbs energy of unfolding in 3 M guanidine hydrochloride varied only from 0.95 to 1.03 times that of the wild-type protein. Moreover, the stability of the protein substituted at this position, which is buried in the interior of the molecule, tended to increase linearly with increasing hydrophobicity of the substituted residue, unless the volume of the substituted residue was over a certain limit. Study holds ProTherm entries: 895, 896, 897, 898, 899, 900, 901, 902, 903, 904, 905, 906, 907, 908, 909, 910, 911, 912, 913, 914, 915, 916, 917, 918, 919, 920, 921, 922, 923, 924, 925, 926, 927, 928, 929, 930, 931, 932 Extra Details: additive : EDTA(0.1 mM),ddG values were measured in the presence of 3M GdnHCl conformational stability; hydrophobicity; Escherichia coli;,alpha subunits of tryptophan synthase; Gibbs energy
Submitter: Connie Wang
Submission Date: April 24, 2018, 8:16 p.m.
|Number of data points||150|
|Proteins||Tryptophan synthase alpha chain ; Tryptophan synthase alpha chain|
|Assays/Quantities/Protocols||Experimental Assay: dG_H2O pH:9.0 ; Experimental Assay: dG pH:9.0 ; Experimental Assay: dG_H2O pH:7.0 ; Experimental Assay: dG pH:7.0 ; Derived Quantity: ddG pH:9.0 ; Derived Quantity: ddG_H2O pH:9.0 ; Derived Quantity: ddG_H2O pH:7.0 ; Derived Quantity: ddG pH:7.0|
|Libraries||Mutations for sequence MERYESLFAQLKERKEGAFVPFVTLGDPGIEQSLKIIDTLIEAGADALELGIPFSDPLADGPTIQNATLRAFAAGVTPAQCFEMLALIRQKHPTIPIGLLMYANLVFNKGIDEFYAQCEKVGVDSVLVADVPVEESAPFRQAALRHNVAPIFICPPNADDDLLRQIASYGRGYTYLLSRAGVTGAENRAALPLNHLVAKLKEYNAAPPLQGFGISAPDQVKAAIDAGAAGAISGSAIVKIIEQHINEPEKMLAALKVFVQPMKAATRS|