The metal binding properties of two chemically synthesized peptides, Ac-Gly-Asp-His-Gly-Cys-Ser-Gly-Ala-Ser-Ser-Cys-Thr-His-Ala-Ser-NH2 and Ac-Pro-Asp-His-Ser-Cys-Ser-Thr-Gly-Gly-Ser-Cys-Thr-His-Thr-Ser-NH2, with coordination sites Cys2His2 werecharacterized. The peptides are based on a metallothionein consensus sequence in which two cysteine residues have been replaced by histidine. Spectrophotometric titrations using Co2+ as a probe indicated that both peptides form 1:1 peptide-Co(II) complexes, and allowed determination of the corresponding affinity constants. The absorption spectrum of the peptide-Co(II) complexes is highly suggestive of tetrahedral coordination involving two cysteine and two histidine residues. Assuming that Zn(II) and Cd(II) have the same coordination environments as Co(II), the affinity constants for the peptide complexes with Zn2+ and Cd2+ were determined via a series of competitive metal ion titrations. For both peptides the trend in relative affinities for the metals studied follows the order Cd(II) ≈ Zn(II) > Co(II). Analogous spectroscopic studies with a third metallothionein-related peptide of sequence Ac-Gly-Asp-Cys-Gly-Asp-Ser-Gly-Ala-Ser-Ser-Cys-Thr-Asp-Ala-Ser-NH2, with a putative coordination site Cys2Asp2, showed that this peptide does not bind Co2+ with tetrahedral geometry. © 1998 Elsevier Science S.A. All rights reserved.
|Journal||Inorganica Chimica Acta|
|Publication status||Published - 15 Aug 1998|
- Cobalt complexes
- Metal binding
- Peptide complexes