Differential scanning calorimetry of thermal unfolding of the methionine repressor protein (MetJ) from Escherichia coli.


The thermal stability of the methionine repressor protein from Escherichia coli (MetJ) has been examined over a wide range of pH (pH 3.5-10) and ionic strength conditions using differential scanning calorimetry. Under reducing conditions, the transitions are fully reversible, and thermograms are characteristic of the cooperative unfolding of a globular protein with a molecular weight corresponding to the MetJ dimer, indicating that no dissociation of this dimeric protein occurs before unfolding of the polypeptide chains under most conditions. In the absence of reducing agent, repeated scans in the calorimeter show only partial reversibility, though the thermodynamic parameters derived from the first scans are comparable to those obtained under fully reversible conditions. The protein is maximally stable (Tm 58.5 degrees C) at about pH 6, close to the estimated isoelectric point, and stability is enhanced by increasing ionic strength in the range I = 0.01-0.4 M. The average calorimetric transition enthalpy (delta Hm) for the dimer is 505 +/- 28 kJ mol-1 under physiological conditions (pH 7, I = 0.125, Tm = 53.2 degrees C) and shows a small temperature dependence which is consistent with an apparent denaturational heat capacity change (delta Cp) of about +8.9 kJ K-1 mol-1. The effects of both pH and ionic strength on the transition temperature and free energy of MetJ unfolding are inconsistent with any single amino acid contribution and are more likely the result of more general electrostatic interactions, possibly including significant contributions from electrostatic repulsion between the like-charged monomers which can be modeled by a Debye-Hückel screened potential. Study holds ProTherm entries: 2958, 11836 Extra Details: dG was calculated at 25 degrees C thermal stability; MetJ; cooperative unfolding; enthalpy;,heat capacity change; electrostatic interactions

Submission Details

ID: do36tS353

Submitter: Connie Wang

Submission Date: April 24, 2018, 8:20 p.m.

Version: 1

Publication Details
Johnson CM;Cooper A;Stockley PG,Biochemistry (1992) Differential scanning calorimetry of thermal unfolding of the methionine repressor protein (MetJ) from Escherichia coli. PMID:1390748
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 Met repressor A7ZUF7 METJ_ECO24
100.0 Met repressor B7UNQ8 METJ_ECO27
100.0 Met repressor B7LA39 METJ_ECO55
100.0 Met repressor P0A8U8 METJ_ECO57
100.0 Met repressor B5Z040 METJ_ECO5E
100.0 Met repressor B7M6Z3 METJ_ECO8A
100.0 Met repressor C5A0A5 METJ_ECOBW
100.0 Met repressor B1XBA4 METJ_ECODH
100.0 Met repressor A8A746 METJ_ECOHS
100.0 Met repressor Q0TAC6 METJ_ECOL5
100.0 Met repressor P0A8U7 METJ_ECOL6
100.0 Met repressor B1IVD9 METJ_ECOLC
100.0 Met repressor P0A8U6 METJ_ECOLI
100.0 Met repressor B6I4T6 METJ_ECOSE
100.0 Met repressor B1LNP3 METJ_ECOSM
100.0 Met repressor B7LUR5 METJ_ESCF3
100.0 Met repressor B2TWD5 METJ_SHIB3
100.0 Met repressor Q31U49 METJ_SHIBS
100.0 Met repressor Q32AD6 METJ_SHIDS
100.0 Met repressor P0A8U9 METJ_SHIFL
100.0 Met repressor Q3YV35 METJ_SHISS
99.0 Met repressor B5F0T1 METJ_SALA4
99.0 Met repressor Q57HB6 METJ_SALCH
99.0 Met repressor B5FPU9 METJ_SALDC
99.0 Met repressor B5QXM8 METJ_SALEP
99.0 Met repressor B5RF72 METJ_SALG2
99.0 Met repressor B4TCN8 METJ_SALHS
99.0 Met repressor B4T0U7 METJ_SALNS
99.0 Met repressor Q5PK48 METJ_SALPA
99.0 Met repressor A9MZJ3 METJ_SALPB
99.0 Met repressor C0Q452 METJ_SALPC
99.0 Met repressor B5BJL6 METJ_SALPK
99.0 Met repressor B4TPW1 METJ_SALSV
99.0 Met repressor Q8Z2Z4 METJ_SALTI
98.1 Met repressor P06203 METJ_SALTY
95.2 Met repressor B5XZ31 METJ_KLEP3
94.3 Met repressor A6TGC7 METJ_KLEP7
94.3 Met repressor A4WG61 METJ_ENT38
94.3 Met repressor A7ML79 METJ_CROS8
93.3 Met repressor Q6CZA0 METJ_PECAS
93.3 Met repressor C6DHN7 METJ_PECCP
91.4 Met repressor Q7MYC7 METJ_PHOLL
91.4 Met repressor Q2NQY6 METJ_SODGM
92.4 Met repressor B2VI92 METJ_ERWT9
93.3 Met repressor A8AKY5 METJ_CITK8
90.5 Met repressor A8GL90 METJ_SERP5
90.5 Met repressor A1JI14 METJ_YERE8
90.5 Met repressor A7FCZ2 METJ_YERP3
90.5 Met repressor B2JZD3 METJ_YERPB
90.5 Met repressor Q66G78 METJ_YERPS
90.5 Met repressor B1JQ68 METJ_YERPY
90.5 Met repressor B4F178 METJ_PROMH