Fourier transform infrared spectroscopic study on the Ca 2+ ‐bound coordination structures of synthetic peptide analogues of the calcium‐binding site III of troponin C

The coordination structures of Ca 2+ ion bound to synthetic peptide analogues of the calcium‐binding site III of rabbit skeletal muscle troponin C (TnC) were investigated by Fourier transform infrared (FTIR) spectroscopy. The region of the COO − antisymmetric stretching vibration provides information about the coordination modes of a COO − group to a metal ion. The 34‐residue peptide corresponding to the EF hand motif (helix–loop–helix) showed a band at 1552 cm −1 in the Ca 2+ ‐loaded state, indicating that the side‐chain COO − group of Glu at the 12th position serves as a ligand for Ca 2+ in the bidentate coordination mode. On the other hand, the 13‐residue peptide (Ac‐DRDADGYIDAEEL‐NH 2 ) containing the Ca 2+ ‐binding site III (DRDADGYIDAEE) did not show such spectral patterns in the Ca 2+ ‐loaded state, meaning that shorter synthetic peptide corresponding to the site III has less or no affinity for Ca 2+ . It was found that the 17‐residue peptide (Ac‐DRDADGYIDAEELAEIF‐NH 2 ) is the minimum peptide necessary for the interaction of side‐chain COO − of Glu at the 12th position with Ca 2+ in the bidentate coordination mode. We discuss the relationship between the amino acid length of synthetic peptide analogues and the formation of Ca 2+ ‐bound coordination structure. © 2006 Wiley Periodicals, Inc. Biopolymers 82: 339–343, 2006 This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com