Unfolding of trp repressor studied using fluorescence spectroscopic techniques.


The unfolding properties of the trp repressor of Escherichia coli have been studied using a number of different time-resolved and steady-state fluorescence approaches. Denaturation by urea was monitored by the average fluorescence emission energy of the intrinsic tryptophan residues of the repressor. These data were consistent with a two-state transition from dimer to unfolded monomer with a free energy of unfolding of 19.2 kcal/mol. The frequency response profiles of the fluorescence emission brought to light subtle urea-induced modifications of the intrinsic tryptophan decay parameters both preceding and following the main unfolding transition. The increase of lifetime induced by urea required higher concentrations of urea than the increase in the total intensity described by Gittelman and Matthews [(1990) Biochemistry 29, 7011]. This indicates that the intensity increase has both dynamic and static origins. To assess the effect of tryptophan binding upon repressor stability, and to determine whether repressor oligomerization would be detectable in an unfolding experiment, we examined denaturation profiles of repressor labeled with the long-lived fluorescence probe 5-(dimethylamino)naphthalene-1-sulfonyl (DNS), by monitoring the average rotational correlation time of the probe. These experiments revealed a protein concentration dependent transition at low urea concentrations. This transition was promoted by tryptophan binding. We ascribe this transition to urea-induced dissociation of repressor tetramers. The main unfolding transition of the dimer to unfolded monomer was also observable using this technique, and the free energies associated with this transition were 18.3 kcal/mol in the absence of tryptophan and 24.1 kcal/mol in its presence, demonstrating that co-repressor binding stabilizes the repressor dimer against denaturation.(ABSTRACT TRUNCATED AT 250 WORDS) Study holds ProTherm entries: 5308 Extra Details: two-state transition; repressor oligomerization; dissociation;,tryptophan binding

Submission Details


Submitter: Connie Wang

Submission Date: April 24, 2018, 8:29 p.m.

Version: 1

Publication Details
Fernando T;Royer CA,Biochemistry (1992) Unfolding of trp repressor studied using fluorescence spectroscopic techniques. PMID:1637807
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