Premium
Stereospecific assignments of 1 H‐nmr methyl lines and conformation of valyl residues in the lac repressor headpiece
Author(s) -
Zuiderweg E. R. P.,
Boelens R.,
Kaptein R.
Publication year - 1985
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.360240402
Subject(s) - chemistry , stereospecificity , lac repressor , amide , stereochemistry , nuclear magnetic resonance spectroscopy , methyl group , nuclear overhauser effect , proton , crystallography , chemical shift , resonance (particle physics) , proton nmr , nuclear magnetic resonance , repressor , group (periodic table) , organic chemistry , biochemistry , physics , quantum mechanics , particle physics , transcription factor , gene , catalysis
Two‐dimensional 1 H‐nmr methods are described to obtain information on the sidechain conformation of valyl residues of the lac repressor headpiece and to assign the resonances of their methyl groups stereospecifically. The spin–spin coupling constants ( J αβ ) between C α and C β protons are obtained from two‐dimensional correlated spectroscopy experiments. Large values for J αβ (10–12 Hz) corresponding to trans orientations for these protons ( g + conformation) are found for all valyl residues in α‐helical segments. For these valyl residues, the distance between one methyl group (γ 1 )and the valyl amide proton is much shorter than for the other methyl group, so that stereospecific resonance assignments follow from relative intensities of the corresponding cross peaks in a two‐dimensional nuclear Overhauser enhancement spectrum. Thus, streospecific assignments could be made for the methyl groups of Val 9, 20, 23, and 38 (of a total of eight valyl residues).