ZINC COORDINATION IN THE DNA-BINDING DOMAIN OF THE YEAST TRANSCRIPTIONAL ACTIVATOR PPR1

The structure of the native zinc form of the DNA binding domain in the yeast transcriptional activator PPR1 was investigated by extended X-r ay absorption fine structure (EXAFS). By carrying out the EXAFS measur ements at 11k we were able to demonstrate explicitly the proximity of the two zinc ions (Zn-Zn distance = 3.16 +/- 0.03 Angstrom) and the pr esence of bridging cysteine ligands. The results show that the six cys teine residues co-ordinate two zinc ions in a two-metal ion cluster. P PR1 is the first member of this class of protein for which such inform ation has been obtained.