Determinants of Binding-site Specificity Among Yeast C6 Zinc Cluster Proteins

Related DNA binding proteins often recognize similar DNA sites but can distinguish among them with the use of different protein-DNA contacts. Here, it is shown that members of the C6 zinc cluster family of yeast transcriptional activators distinguish related DNA sites by a different mechanism. The DNA binding site for each of these proteins contains identical nucleotide triplets (CGG ... CCG) but differs in the spacings between the triplets. It is shown that zinc clusters of these proteins work interchangeably to recognize the conserved triplets and that the region 19 amino acids to the carboxyl-terminal side of the zinc cluster, comprising the linker and the beginning of a dimerization element as inferred from the GAL4 crystal structure, directs the protein to its preferred site.