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

Abstract The structure of the native zinc form of the DNA binding domain in the yeast transcriptional activator PPR1 was investigated by extended X-ray absorption fine structure (EXAFS). By carrying out the EXAFS measurements at 11k we were able to demonstrate explicitly the proximity of the two zinc ions ( ZnZn distance = 3.16 ± 0.03 A ) and the presence of bridging cysteine ligands. The results show that the six cysteine residues co-ordinate two zinc ions in a two-metal ion cluster. PPR1 is the first member of this class of protein for which such information has been obtained.