Cooperative binding of λ repressors to sites separated by integral turns of the DNA helix

摘要: Lambda repressors bind cooperatively to adjacent pairs of operator sites. Here we show that sites whose centers have been separated by five or six turns the helix. No cooperativity is observed when these are on opposite sides DNA Cooperativity depends upon same part protein (the carboxyl domain) mediates adjacent. As bind, between becomes alternately sensitive and resistant DNAase I cleavage at half turn intervals. We suggest sites, forms a loop, thus allowing two touch.