High-resolution proton nuclear magnetic resonance studies of the exchangeable resonances of the lac repressor headpiece

Sequence-specific resonance assignments in the 1H nuclear-magnetic-resonance spectrum of the lac repressor DNA-binding domain 1-51 from Escherichia coli by two-dimensional spectroscopy

The assignment of the 1H nuclear magnetic resonance (NMR) spectrum of the DNA-binding domain 1-51 of lac repressor from Escherichia coli is described and documented. The assignments are based entirely on the amino acid sequence and on two-dimensional NMR experiments at 360 MHz and 500 MHz. Individual assignments were obtained at 18 degrees C for the backbone protons of 44 out of the total of 51 amino acids residues, the exceptions being Met-1, Lys-2, Tyr-7, Arg-35, Glu-36, Lys-37 and Ile-48. Complete assignments of the non-labile hydrogen atoms of the side chain were obtained for 33 residues, and for Asn-46 and Asn-50 the delta amide protons were also identified. The chemical shifts for the assigned resonances at 18 degrees C are listed for an aqueous solution at pH 4.9 and at pH 6.8.

Secondary structure of the lac repressor DNA-binding domain by two-dimensional 1H nuclear magnetic resonance in solution

A recently proposed approach for spatial structure determination in noncrystalline proteins by nuclear magnetic resonance was applied to the lac repressor DNA-binding domain. On the basis of sequence-specific 1H NMR assignments, the location of alpha-helices in the amino acid sequence was determined from nuclear Overhauser enhancement data and from amide proton exchange studies. These investigations provide detailed experimental data on the structure of a noncrystalline DNA-binding protein. The results support the hypothesis advanced by others that sequence-specific interactions between lac repressor and DNA are mediated by a particular spatial arrangement of two alpha-helices common to various different DNA-binding proteins.