title: Variants of a cloned synthetic lactose operator. I. A palindromic dimer lactose operator derived from one stand of the cloned 40-base pair operator.
abstract: Starting with one strand of the 40-bp synthetic operator (Sadler et al., 1978), we have constructed and cloned a 66-bp, palindromic DNA segment with the following sequence (Formula: see text), where the horizontal arrows indicate the locations of the two 21-bp "core" operator sequences in this segment and the vertical arrow designates the dyad axis of symmetry. Upon denaturation and rapid renaturation, each strand of this fragment forms a hairpin molecule still retaining an EcoRI cohesive end. Two hairpin molecules can be joined with T4 DNA ligase to form a duplex DNA molecule having no ends (dumbbell form A). Denaturation and rapid renaturation of dumbbell A yields a mixture of two dumbbell forms: dumbbell A which is a substrate for Eco RI, and a new form, dumbbell B, which is not a substrate. Each of the conformations of this DNA fragment have been purified and all are active in binding lactose repressor in vitro.
mesh_terms: D001483:Base Sequence; D003001:Cloning, Molecular / Q000379:methods; D004269:DNA, Bacterial / Q000138:chemical synthesis / Q000235:genetics; D004274:DNA, Recombinant / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics; D007763:Lac Operon; D009690:Nucleic Acid Conformation; D009876:Operon; D010957:Plasmids; D012097:Repressor Proteins / Q000378:metabolism
chemical_list: D004269:DNA, Bacterial; D004274:DNA, Recombinant; D012097:Repressor Proteins