Folding and stability of trp aporepressor from Escherichia coli.


Equilibrium and kinetic studies of the urea-induced unfolding of trp aporepressor from Escherichia coli were performed to probe the folding mechanism of this intertwined, dimeric protein. The equilibrium unfolding transitions at pH 7.6 and 25 degrees C monitored by difference absorbance, fluorescence, and circular dichroism spectroscopy are coincident within experimental error. All three transitions are well described by a two-state model involving the native dimer and the unfolded monomer; the free energy of folding in the absence of denaturant and under standard-state conditions is estimated to be 23.3 +/- 0.9 kcal/mol of dimer. The midpoint of the equilibrium unfolding transition increases with increasing protein concentration in the manner expected from the law of mass action for the two-state model. We find no evidence for stable folding intermediates. Kinetic studies reveal that unfolding is governed by a single first-order reaction whose relaxation time decreases exponentially with increasing urea concentration and also decreases with increasing protein concentration in the transition zone. Refolding involves at least three phases that depend on both the protein concentration and the final urea concentration in a complex manner. The relaxation time of the slowest of these refolding phases is identical with that for the single phase in unfolding in the transition zone, consistent with the results expected for a reaction that is kinetically reversible. The two faster refolding phases are presumed to arise from slow isomerization reactions in the unfolded form and reflect parallel folding channels. Study holds ProTherm entries: 3673 Extra Details: additive : Na2EDTA(0.1 mM),

Submission Details


Submitter: Connie Wang

Submission Date: April 24, 2018, 8:22 p.m.

Version: 1

Publication Details
Gittelman MS;Matthews CR,Biochemistry (1990) Folding and stability of trp aporepressor from Escherichia coli. PMID:2223756
Additional Information

Structure view and single mutant data analysis

Study data

No weblogo for data of varying length.
Colors: D E R H K S T N Q A V I L M F Y W C G P

Data Distribution

Studies with similar sequences (approximate matches)

Correlation with other assays (exact sequence matches)

Relevant UniProtKB Entries

Percent Identity Matching Chains Protein Accession Entry Name
100.0 Trp operon repressor A7ZVT5 TRPR_ECO24
100.0 Trp operon repressor B7LEN9 TRPR_ECO55
100.0 Trp operon repressor P0A882 TRPR_ECO57
100.0 Trp operon repressor B5Z4S5 TRPR_ECO5E
100.0 Trp operon repressor B7LXV6 TRPR_ECO8A
100.0 Trp operon repressor C4ZT75 TRPR_ECOBW
100.0 Trp operon repressor B1XFK3 TRPR_ECODH
100.0 Trp operon repressor A8A8C2 TRPR_ECOHS
100.0 Trp operon repressor B1IS26 TRPR_ECOLC
100.0 Trp operon repressor P0A881 TRPR_ECOLI
100.0 Trp operon repressor B6I6P1 TRPR_ECOSE
100.0 Trp operon repressor B2TZS6 TRPR_SHIB3
100.0 Trp operon repressor Q31SU5 TRPR_SHIBS
100.0 Trp operon repressor Q327K2 TRPR_SHIDS
100.0 Trp operon repressor Q0SX19 TRPR_SHIF8
100.0 Trp operon repressor P0A883 TRPR_SHIFL
100.0 Trp operon repressor Q3YU01 TRPR_SHISS
99.1 Trp operon repressor B7UR23 TRPR_ECO27
99.1 Trp operon repressor B7MNK2 TRPR_ECO45
99.1 Trp operon repressor B7N2W3 TRPR_ECO81
99.1 Trp operon repressor A1AJW2 TRPR_ECOK1
99.1 Trp operon repressor Q0T8R8 TRPR_ECOL5
99.1 Trp operon repressor Q8FA42 TRPR_ECOL6
99.1 Trp operon repressor Q1R248 TRPR_ECOUT
100.0 Trp operon repressor B7NW74 TRPR_ECO7I
100.0 Trp operon repressor B7NH68 TRPR_ECOLU
100.0 Trp operon repressor B7LNT5 TRPR_ESCF3
99.1 Trp operon repressor B1LEK0 TRPR_ECOSM
90.4 Trp operon repressor A9MR96 TRPR_SALAR