+ Site Statistics
+ Search Articles
+ PDF Full Text Service
How our service works
Request PDF Full Text
+ Follow Us
Follow on Facebook
Follow on Twitter
Follow on LinkedIn
+ Subscribe to Site Feeds
Most Shared
PDF Full Text
+ Translate
+ Recently Requested

Calorimetric study of tryptophan synthase alpha-subunit and two mutant proteins



Calorimetric study of tryptophan synthase alpha-subunit and two mutant proteins



International Journal of Peptide and Protein Research 20(4): 331-336



Heat-denaturation of tryptophan synthase alpha-subunit from E. coli and two mutant proteins (Glu 49 leads to Gln or Ser; called Gln 49 or Ser 49, respectively) has been studied by the scanning microcalorimetric method at various pH, in an attempt to elucidate the role of individual amino acid residues in the conformational stability of a protein. The partial specific heat capacity in the native state at 20 degrees, Cp20, has been found to be (0.43 +/- 0.02) cal . k-1 . g-1, the unfolding heat capacity change, delta dCp, (0.10 +/- 0.01) cal . K-1 . g-1, and the unfolding enthalpy value extrapolated to 110 degrees, delta dh110, (9.3 +/- 0.5) cal . g-1 for the three proteins. The value of Cp20 was larger than those found for "fully compact protein" and that of delta dh110 was smaller. Unfolding Gibbs energy, delta dG at 25 degrees for Wild-type, Gln 49, and Ser 49 were 5.8, 8.4, and 7.1 kcal . mol-1 at pH 9.3, respectively. Unfolding enthalpy, delta dH, of the three proteins seemed to be the same and equal to (23.2 +/- 1.2) kcal . mol-1 at 25 degrees. As a consequence of the same value of delta dH and the different value in delta dG, substantial differences in unfolding entropy, delta dS, were found for the three proteins. The values of delta dG for the three proteins at 25 degrees coincided with those from equilibrium methods of denaturation by guanidine hydrochloride.

Please choose payment method:






(PDF emailed within 1 workday: $29.90)

Accession: 042436396

Download citation: RISBibTeXText

PMID: 6816746


Related references

Calorimetric study of tryptophan synthase alpha subunit and 2 mutant proteins. International Journal of Peptide & Protein Research 20(4): 331-336, 1982

Calorimetric study of tryptophan synthase α-subunit and two mutant proteins. Chemical Biology & Drug Design 20(4): 331-336, 1982

Folding of mutant tryptophan synthase alpha subunit proteins. Federation Proceedings 45(6): 1919, 1986

Evidence that glutamic acid 49 of tryptophan synthase alpha subunit is a catalytic residue. Inactive mutant proteins substituted at position 49 bind ligands and transmit ligand-dependent to the beta subunit. Journal of Biological Chemistry 263(18): 8611-8614, 1988

PH dependence of stability of the wild-type tryptophan synthase alpha-subunit and two mutant proteins (Glu49 replaced by Met or Gln). Journal of Molecular Biology 144(4): 455-465, 1980

Substrate interactions with the alpha-subunit of the Escherichia coli tryptophan synthase. A study of the activity of mutant alpha-subunits. Archives of Biochemistry and Biophysics 181(2): 428-437, 1977

Conformational changes in the alpha-subunit coupled to binding of the beta 2-subunit of tryptophan synthase from Escherichia coli: crystal structure of the tryptophan synthase alpha-subunit alone. Biochemistry 44(4): 1184-1192, 2005

Ph dependence of stability of the wild type tryptophan synthase alpha subunit and 2 mutant proteins glutamic acid 49 methionine or glutamine. Journal of Molecular Biology 144(4): 455-466, 1980

Effect of amino acid residues on conformational stability in eight mutant proteins variously substituted at a unique position of the tryptophan synthase alpha-subunit. Journal of Biological Chemistry 259(22): 14076-14081, 1984

Subunit interaction in tryptophan synthase of Escherichia coli: calorimetric studies on association of alpha and beta 2 subunits. Biochemistry 18(10): 1979-1984, 1979

Comparison of denaturation by guanidine hydro chloride of the wild type tryptophan synthase ec 4.2.1.20 alpha subunit of escherichia coli and 2 mutant proteins glutamic acid 49 replaced by methionine or glutamine. Journal of Biochemistry 85(4): 915-922, 1979

Synergism in folding of a double mutant of the alpha subunit of tryptophan synthase. Biochemistry 25(21): 6356-6360, 1986

State of Tyr49 in a mutant tryptophan synthase alpha-subunit substituted at position 49. Journal of Biochemistry 88(6): 1733-1738, 1980

Evidence that glutamic acid 49 of tryptophan synthase a subunit is a catalytic residue. Inactive mutant proteins substituted at position 49 bind ligands and transmit ligand-dependent effects to the b subunit. The Journal of Biological Chemistry 263: 11-14, 1988

Substrate interactions with the alpha-subunit of the Escherichia coli tryptophan synthase. A kinetic study of the wild-type alpha-subunit. Archives of Biochemistry and Biophysics 181(2): 419-427, 1977