[Formation of recognition site in transcription factors: repressor of phage lambda and a murine immunoglobulin...

IPolar interactions between protein and the major groove of double-stranded DNA have been analyzed on the basis of a structural study of the complexes formed by two transcription factors: phage lambda repressor and murine immunoglobulin transcription factor NF kappa B-p50. Two identical molecules of these two factors form two binding sites within two different parts of a single DNA molecule. This allows one to study formation of the recognition module by comparing the binding pattern of two different parts of the DNA operator. We have shown that formation of the DNA-binding sites for the three structurally different protein domains (one in repressor and two in the immunoglobulin factor) involves polar residues selected from the largest polar cluster on the surface of the protein molecule. It was also shown that the same polar residues bind with different points of DNA sites. This result provides understanding of the recognition module adaptation to varying nucleotide sequence of the operator sites and shows the way of binding site formation.