1H NMR study of the interaction of bacteriophage lambda Cro protein with the OR3 operator. II. Assignment of the non-exchangeable proton resonances of the OR3 operator.

The 17 base pair operator OR3 oligonucleotide, which is the preferential binding site for the Cro repressor of phage lambda, was studied by two-dimensional NMR spectroscopy. A sequential assignment procedure based on two-dimensional Nuclear Overhauser Effect (NOESY) and scalar coupling correlated (COSY) NMR spectroscopy, together with the knowledge of the oligodesoxynucleotide sequence, made it possible to assign the non-exchangeable base protons and the H1' and the H2'-H2" sugar protons of the OR3 operator DNA. The pattern of the observed NOE connectivities is consistent with a right-handed helical DNA structure. The base and sugar proton assignments provide the necessary information for further studies of the OR3 operator - Cro repressor interaction.