| Title | Thermal denaturation of the core protein of lac repressor. | | Author(s) | Manly SP, Matthews KS, Sturtevant JM | | Source | Biochemistry 1985 Jul 16; 24(15):3842-6. | | MeSH | Calorimetry, Differential Scanning
Escherichia coli
Glycosides
Isopropyl Thiogalactoside
Ligands
Protein Conformation
Protein Denaturation
Repressor Proteins
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.
Research Support, U.S. Gov't, P.H.S.
Thermodynamics
Transcription Factors
| | Abstract | The thermal denaturation of the core protein of lac repressor was studied alone and in the presence of the inducer isopropyl beta-D-thiogalactoside (IPTG) and the antiinducer o-nitrophenyl beta-D-fucoside (ONPF) by means of high-sensitivity differential scanning calorimetry. The denaturation that takes place at about 65 degrees C is apparently irreversible; i.e., a rescan of a previously scanned sample of protein solution shows no denaturational endotherm. Despite this irreversibility, the denaturation appeared to follow quantitatively the dictates of equilibrium thermodynamics as embodied in the van't Hoff equation. The results obtained indicate clearly that the tetrameric protein dissociates to monomers during denaturation and that the ligands are not dissociated until denaturation takes place. The enthalpy of denaturation of the protein is 4.57 +/- 0.25 cal g-1 and is independent of temperature. The enthalpies of dissociation of IPTG and ONPF at the denaturation temperature are very large, 37 and 42 kcal (mol of ligand)-1, respectively. | | Language | eng | | Pub Type(s) | Journal Article
| | PubMed ID | 3902076 |
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