title: Multiphasic denaturation of the lambda repressor by urea and its implications for the repressor structure.
abstract: Urea denaturation of the lambda repressor has been studied by fluorescence and circular dichroic spectroscopies. Three phases of denaturation could be detected which we have assigned to part of the C-terminal domain, N-terminal domain and subunit dissociation coupled with further denaturation of the rest of the C-terminal domain at increasing urea concentrations. Acrylamide quenching suggests that at least one of the three tryptophan residues of the lambda repressor is in a different environment and its emission maximum is considerably blue-shifted. The transition in low urea concentration (midpoint approximately 2 M) affects the environment of this tryptophan residue, which is located in the C-terminal domain. Removal of the hinge and the N-terminal domain shifts this transition towards even lower urea concentrations, indicating the presence of interaction between hinge on N-terminal and C-terminal domains in the intact repressor.
authors.affiliation: Department of Biophysics, Bose Institute, Calcutta, India.
authors.forename: U
authors.initials: U
authors.lastname: Banik
authors.forename: R
authors.initials: R
authors.lastname: Saha
authors.forename: N C
authors.initials: NC
authors.lastname: Mandal
authors.forename: B
authors.initials: B
authors.lastname: Bhattacharyya
authors.forename: S
authors.initials: S
authors.lastname: Roy
mesh_terms: D004268:DNA-Binding Proteins; D004926:Escherichia coli / Q000378:metabolism; D007700:Kinetics; D010446:Peptide Fragments / Q000302:isolation & purification; D011487:Protein Conformation; D011489:Protein Denaturation; D012097:Repressor Proteins / Q000737:chemistry* / Q000187:drug effects; D013050:Spectrometry, Fluorescence; D013438:Sulfhydryl Compounds / Q000378:metabolism; D014157:Transcription Factors / Q000737:chemistry; D014364:Tryptophan; D014508:Urea / Q000494:pharmacology*; D014764:Viral Proteins; D054334:Viral Regulatory and Accessory Proteins
chemical_list: D004268:DNA-Binding Proteins; D010446:Peptide Fragments; D012097:Repressor Proteins; D013438:Sulfhydryl Compounds; D014157:Transcription Factors; D014764:Viral Proteins; D054334:Viral Regulatory and Accessory Proteins; C016649:phage repressor proteins; D014364:Tryptophan; D014508:Urea