title: NMR studies of the trp repressor from Escherichia coli. Characterisation and assignments of residue types.
abstract: High-resolution proton nuclear magnetic resonance spectra of the trp repressor of Escherichia coli under various conditions are reported and analysed. The spectrum of the denatured state agrees with that predicted from the amino acid composition, with the exception of the two histidine residues, which have different chemical shifts although they titrate normally. The spectrum of the native protein shows the presence of extensive secondary and tertiary structure. Using information from chemical shifts, numbers of protons, titration behaviour, homonuclear chemical-shift-correlated spectroscopy and nuclear Overhauser enhancement correlated spectroscopy, most of the aromatic protons have been assigned to residue type. Further, about 30% of the aliphatic protons have been assigned to residue type by two-dimensional spectroscopy. Nuclear Overhauser enhancements establish that high-field methyl groups belonging to a valine residue lie directly over an aromatic ring.
mesh_terms: D001426:Bacterial Proteins; D055598:Chemical Phenomena; D002621:Chemistry; D004578:Electron Spin Resonance Spectroscopy; D004926:Escherichia coli / Q000235:genetics*; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D011489:Protein Denaturation; D011522:Protons; D012097:Repressor Proteins / Q000032:analysis*; D013696:Temperature; D014157:Transcription Factors / Q000032:analysis*; D014508:Urea; D029968:Escherichia coli Proteins
chemical_list: D001426:Bacterial Proteins; D011522:Protons; D012097:Repressor Proteins; D014157:Transcription Factors; D014508:Urea; C027190:TRPR protein, E coli; D029968:Escherichia coli Proteins