Interaction of arsenite with a zinc finger CCHC peptide: Evidence for formation of an As–Zn-peptide mixed complex

The interaction of arsenite with a Cys3His (CCHC) zinc finger model (34–51) HIV-1 nucleocapsid protein p7 (NCp7) peptide in the absence and presence of ZnII was studied using fluorescence spectroscopy, CD (circular dichroism) and ESI-MS (Electrospray Ionization Mass Spectrometry). We found that arsenic forms different complexes with the free peptide and the zinc finger peptide. In the former case the peptide conformation differed greatly from that of the zinc finger, whereas in the second case a mixed As–Zn-peptide complex was formed with partial preservation of zinc finger conformation. An apparent stability constant was estimated for the mixed As–Zn-peptide complex (K = 2083 M− 1 and 442 M− 1 at 25 °C and pHs 6 and 7, respectively). Our study also shows that the interaction of arsenic with the CCHC motif is facilitated by glutathione (GSH), through formation of a GS–As-peptide conjugate.

Fluorescence spectroscopy, circular dichroism and ESI-MS show the formation of As–ZF-peptides upon arsenite incubation with a Cys3His zinc finger.Figure optionsDownload as PowerPoint slide