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

In order to study the mode of action of the tof gene product, which is an "autorepressor" of the bacteriophage lambda and plasmid lambdadv, we have purified a DNA-binding protein which is specifically produced in bacteria carrying lambdadv. 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 lambda 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 lambdaDNA-specific binding protein is not produced in cells carrying i21dv or ø80dv.