Purification and properties of a λ operator-binding protein which is expected to be autorepressor (tof protein) from E. coli carrying λdv plasmid

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Abstract
In order to study the mode of action of the tof gene product, which is an “autorepressor” of the bacteriophage λ and plasmid λdv, we have purified a DNA-binding protein which is specifically produced in bacteria carrying λdv. This protein possesses characteristics expected for the product of the tof gene, since it is produced under conditions where cI-repressor is not made, and since it binds to oL and oR operators on the λ phage genome. The molecular weight of the native protein is 16,000–17,000 daltons, and the monomeric molecular weight as measured by gel electrophoresis in the presence of sodium dodecyl sulfate is about 10,000 daltons. Denaturation and renaturation experiments demonstrated that the native protein is a dimer of 10,000-dalton monomers. The λDNA-specific binding protein is not produced in cells carrying i 21dv or Φ80dv.