A VARIANT OF LAMBDA-REPRESSOR WITH AN ALTERED PATTERN OF COOPERATIVE BINDING TO DNA SITES

The bacteriophage lambda repressor binds cooperatively to pairs of adj acent sites in the lambda chromosome, one repressor dimer binding to e ach site, The repressor's amino domain (that which mediates DNA bindin g) is connected to its carboxyl domain (that which mediates dimerizati on and the interaction between dimers) by a protease-sensitive linker region, We have generated a variant A repressor that lacks this linker region, We show that dimers of the variant protein are deficient in c ooperative binding to sites at certain, but not all, distances, The li nker region thus extends the range over which carboxyl domains of DNA- bound dimers can interact. In particular, the linker is required for c ooperative binding to a pair of sites as found in the lambda chromosom e, and thus is essential for the repressor's physiological function.