In the present study, the binding properties of Sb(III) was compared between CCCH- and CCHC-type zinc-finger peptides derived from kinetoplastid proteins. 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. The present study establishes for the first time that Sb(III) more effectively displaces Zn(II) from a CCCH-type peptide than from CCHC-type peptide, as a result of both greater stability of Sb(III)-CCCH complex (compared to Sb-CCHC complexes) and lower stability of Zn-CCCH complex (compared to Zn-CCHC complexes). Our data also supports the model that not only the conserved zinc finger motif (CCCH or CCHC), but also the sequence of non-conserved amino-acids, determines the binding affinity of Sb(III) and Zn(II).  This data suggests that the interaction of Sb(III) with CCCH-type zinc finger protein may modulate, or even mediate, the pharmacological action of antimonial drugs.

Greater binding affinity of Sb(III) to a CCCH zinc finger domain compared to a CCHC domain of kinetoplastid proteins

243rd National Meeting (2012)

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