Synthesis and characterization of a sequence-specific DNA-binding protein that contains ruthenium polypyridyl centers

A chimeric metallo-bZIP protein, (GBR-CC)Ru, was prepared that contains the native DNA-binding domain of the GCN-4 transcription factor (GBR), a synth etic alpha-helical coiled-coil dimerization site (CC), and a ruthenium poly pyridyl complex (Ru) attached to a surface-exposed cysteine residue. The ph otophysical properties of the peptide-bound ruthenium complex include a lon g-lived emission that is shortened when the peptide is dissolved in air-sat urated water. Electrophoretic mobility shift assays show that the chimeric metalloprotein also retains the essential DNA recognition properties of the native GCN-4 transcriptional activator. Peptide-DNA complexes are formed w ith the related AP1 and CRE sequences, but not the divergent Spl sequence. Peptide titration studies indicate that the affinities of (GBR-CC)Ru for th e AP1 and CRE sites are comparable. Steady-state photolysis experiments sho w that (GBR-CC)Ru does not produce photoinduced DNA damage, probably due to the separation distance between the ruthenium sites and the DNA. bases. (C ) 2000 Elsevier Science S.A. All rights reserved.