MG2-SPECIFIC BINDING OF TRANSCRIPTIONAL ACTIVATOR PROTEIN-C OF BACTERIOPHAGE-MU TO DNA( MEDIATED SEQUENCE)

The contributions from the secondary structure of the transcriptional activator protein C of bacteriophage Mu to its specific DNA binding an d the influence of various factors, viz., electrolytes, and minor groo ve and major groove binders on this protein-DNA interaction have been addressed. Circular dichroism (CD) spectral results suggest that, in t he absence of Mg2+, C protein exhibits a P-pleated sheetlike structure and Mg2+ changes the conformation to a more ex-helical structure whic h could provide specific geometrical constraints complementary to thos e of DNA helix. Thus, Mg2+ acts as a cofactor for the binding of the C protein to its specific site in DNA by inducing conformational change s in the protein. Competitive binding studies with minor and major gro ove binding drugs, viz., distamycin A and methyl green, respectively, and the DMS footprinting data indicate that the C protein recognizes t he major groove of DNA during complex formation. Further, upon major g roove binding, C protein brings about changes in DNA conformation; suc h conformational changes could have implications in the transcription process.