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The lac repressor of Escherichia coli controls expression of enzymes involved in lactose metabolism by its interactions with inducer and with specific and nonspecific DNA. This has long been the model system for understanding transcriptional control. In his Perspective, von Hippel describes new work by Kalodimos et al. that completes the structural picture of the lac repressor system by providing a structure of the complex with nonspecific DNA. Pleasingly, the structure validates previous predictions of how the repressor binds to nonspecific DNA and how it locates its operator target site.