title: Greater binding affinity of trivalent antimony to a CCCH zinc finger domain compared to a CCHC domain of kinetoplastid proteins.
abstract: It has been reported recently that Sb(III) competes with Zn(II) for its binding to the CCHC zinc finger domain of the HIV-1 NCp7 protein, suggesting that zinc finger proteins may be molecular targets for antimony-based drugs. Here, the interaction of Sb(III) with a CCCH zinc finger domain, which is considered to play a crucial role in the biology of kinetoplastid protozoa, has been characterized for the first time. The binding characteristics of Sb(III) were compared between a CCCH-type peptide derived from a kinetoplastid protein and two different CCHC-type zinc finger peptides. The formation of 1 : 1 Zn-peptide and Sb-peptide complexes from the different peptides was demonstrated using circular dichroism, UV absorption, fluorescence spectroscopies and ESI-MS. Titration of the Zn-peptide complexes with SbCl(3) was performed at pH 6 and 7, exploiting the intrinsic fluorescence of the peptides. The differential spectral characteristics of the peptides allowed for competition experiments between the different peptides for binding of Zn(II). The present study establishes that Sb(III) more effectively displaces Zn(II) from the CCCH peptide than CCHC ones, as a result of both the greater stability of the Sb-CCCH complex (compared to Sb-CCHC complexes) and the lower stability of the Zn-CCCH complex (compared to Zn-CCHC complexes). Comparison of the binding characteristics of Sb(III) or Zn(II) between the CCHC-type peptides with different amino acid sequences supports the model that not only the conserved zinc finger motif, but also the sequence of non-conserved amino acids determines the binding affinity of Sb(III) and Zn(II). These data suggest that the interaction of Sb(III) with CCCH-type zinc finger proteins may modulate, or even mediate, the pharmacological action of antimonial drugs.
authors.affiliation: Departamento de Fisiologia e Biofísica, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Av Antônio Carlos 6627, Pampulha, 31270-901 Belo Horizonte, Minas Gerais, Brazil. frezard@icb.ufmg.br
authors.forename: Frédéric
authors.initials: F
authors.lastname: Frézard
authors.forename: Heveline
authors.initials: H
authors.lastname: Silva
authors.forename: Adriano Monteiro de Castro
authors.initials: AM
authors.lastname: Pimenta
authors.forename: Nicholas
authors.initials: N
authors.lastname: Farrell
authors.forename: Cynthia
authors.initials: C
authors.lastname: Demicheli
mesh_terms: D000595:Amino Acid Sequence; D000965:Antimony / Q000737:chemistry / Q000378:metabolism*; D002942:Circular Dichroism; D018320:Leishmania major / Q000737:chemistry / Q000378:metabolism; D008969:Molecular Sequence Data; D010455:Peptides; D011485:Protein Binding; D015800:Protozoan Proteins / Q000737:chemistry / Q000378:metabolism*; D021241:Spectrometry, Mass, Electrospray Ionization; D014346:Trypanosoma brucei brucei / Q000737:chemistry / Q000378:metabolism; D015032:Zinc / Q000737:chemistry / Q000378:metabolism*; D016335:Zinc Fingers
chemical_list: D010455:Peptides; D015800:Protozoan Proteins; D000965:Antimony; D015032:Zinc