title: Characterization of the copper- and silver-thiolate clusters in N-terminal fragments of the yeast ACE1 transcription factor capable of binding to its specific DNA recognition sequence.
abstract: N-terminal fragments of ACE1 protein spanning residues 1-122 or 1-110, termed ACE1(122*) and ACE1(110*), respectively, were investigated in regard to their metal- and double-stranded DNA-binding properties. Band mobility shift assays showed that binding to a specific oligonucleotide (termed UASc), containing two ACE1(122*) binding sites, requires the presence of Cu(I) or Ag(I) but does not occur in the presence of divalent metal ions. Both the Ag(I) and the Cu(I) forms of ACE1(122*) were characterized spectroscopically. The Tyr and metal cluster luminescence emission of Cu-ACE1(122*) was specifically quenched by the oligonucleotide UAScL, but not by an oligonucleotide of the same length and base composition but scrambled sequence. The room-temperature luminescence of Cu(I)-ACE1(122*) was assigned to a phosphorescence emission, on the basis of its long-lived luminescence of approximately 3.5 microseconds. We report the first observation of a Ag(I) metal cluster in solution for Ag(I)-ACE1(122*), which was found to exhibit a quantum yield and average luminescence lifetime that are ca. 6% of that of Cu(I)-ACE1(122*). The three-dimensional structure brought about by the binding of either metal ion appears to be very similar, since dynamic tyrosine fluorescence lifetime measurements, as well as circular dichroism spectra, were nearly identical for Cu- and Ag-ACE1(122*). Based on these results, we present a hypothetical model for the structure of the metal cluster in this class of proteins.
authors.affiliation: Department of Chemistry and Biochemistry, University of Maryland, Baltimore County 21228.
authors.forename: J R
authors.initials: JR
authors.lastname: Casas-Finet
authors.forename: S
authors.initials: S
authors.lastname: Hu
authors.forename: D
authors.initials: D
authors.lastname: Hamer
authors.forename: R L
authors.initials: RL
authors.lastname: Karpel
mesh_terms: D001483:Base Sequence; D001665:Binding Sites; D002942:Circular Dichroism; D003300:Copper / Q000737:chemistry*; D004268:DNA-Binding Proteins / Q000737:chemistry*; D005656:Fungal Proteins / Q000737:chemistry*; D008163:Luminescent Measurements; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides / Q000737:chemistry / Q000378:metabolism*; D011487:Protein Conformation; D011994:Recombinant Proteins; D012045:Regulatory Sequences, Nucleic Acid; D012441:Saccharomyces cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D012834:Silver / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet; D014157:Transcription Factors / Q000737:chemistry*; D014364:Tryptophan / Q000737:chemistry
chemical_list: C060256:CUP2 protein, S cerevisiae; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D009838:Oligodeoxyribonucleotides; D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D012834:Silver; D003300:Copper; D014364:Tryptophan