Solution structure of the kluyveromyces lactis LAC9 Cd2 CYs6 DNA-binding domain

The Zn₂Cys₆ DNA-binding domain has been identified by sequence homology in approximately forty fungal proteins, including the K. lactis LAC9 transcriptional activator. Using 1H NMR spectroscopy, we have determined the solution structure of a cadmium-substituted form of the LAC9 DNA-binding domain. We have complemented this approach by applying a series of ¹¹³Cd-¹H NMR experiments, including several novel heteroTOCSY-based techniques. The DNA-binding domain forms a core of two α-helix/extended strand segments around the Cd₂ binudear cluster, with a network of amide proton-cysteinyl Sγ hydrogen bonds stablizing the cluster. Comparison with other Zn₂Cys₆ domain structures provides insight into the common structural elements used in metal coordination and DNA binding.