title: Specificity of the weak binding between the phage SPO1 transcription-inhibitory protein, TF1, and SPO1 DNA.
abstract: The interaction of the phage SPO1 protein transcription factor 1 (TF1), with DNA has been analyzed by membrane filter binding and by sedimentation methods. Substantially specific binding of TF1 to helical SPO1 DNA can be demonstrated by nitrocellulose filter-binding assays at relatively low ionic strength (0.08). However, TF1-DNA complexes dissociate and reequilibrate relatively rapidly and this makes filter-binding assays unsuitable for quantitative measurements of binding equilibra. Accordingly, the sedimentation properties of TF1-DNA complexes have been explored and a short-column centrifugation assay has been elaborated for quantitative measurements. Preferential binding of TF1 to the hydroxymethyluracil-containing SPO1 DNA has also been demonstrated by short-column centrifugation. TF1 binds relatively weakly and somewhat cooperatively to SPO1 DNA at many sites; TF1-DNA complexes dissociate and reequilibrate rapidly. At 20 degrees C in 0.01 M phosphate, pH 7.5, 0.15 KC1, one molecule of TF1 can bind to approximately every 60 nucleotide pairs of SPO1 DNA.
mesh_terms: D001412:Bacillus subtilis / Q000378:metabolism*; D001435:Bacteriophages / Q000378:metabolism*; D001665:Binding Sites; D001667:Binding, Competitive; D004279:DNA, Viral / Q000378:metabolism; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D008970:Molecular Weight; D011485:Protein Binding; D014158:Transcription, Genetic; D014764:Viral Proteins / Q000378:metabolism
chemical_list: D004279:DNA, Viral; D014764:Viral Proteins; D008274:Magnesium