The specific aims of this NMR study of the DNA recognition by EcoRI endonuclease are to obtain an overall conformational characterization of the DNA substrates of EcoRI endonuclease and to elucidate the effects of single-site structural changes at the protein-DNA interface upon the conformation of the DNA-EcoRI endonuclease complex. The EcoRI restriction endonuclease represents one of the most valuable model systems to investigate the molecular basis of the recognition of DNA sequences by genome regulatory proteins. The enzyme recognizes with high specificity the double stranded DNA sequence d(GAATTC) which it cleaves at the GpA bonds. The catalytic activity of EcoRI endonuclease requires magnesium ions as a cofactor. In the absence of magnesium, the enzyme still recognizes the sequence. Due to this property, specific complexes between the protein and synthetic oligonucleoties containing the EcoRI recognition site can be prepared and studied.***
