Fourier transform infrared spectroscopic study on the Ca2+-bound coordination structures of synthetic peptide analogues of the calcium-binding site III of troponin C

The coordination structures of Ca2+ 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 Ca2+-loaded state, indicating that the side-chain COO− group of Glu at the 12th position serves as a ligand for Ca2+ in the bidentate coordination mode. On the other hand, the 13-residue peptide (Ac-DRDADGYIDAEEL-NH2) containing the Ca2+-binding site III (DRDADGYIDAEE) did not show such spectral patterns in the Ca2+-loaded state, meaning that shorter synthetic peptide corresponding to the site III has less or no affinity for Ca2+. It was found that the 17-residue peptide (Ac-DRDADGYIDAEELAEIF-NH2) is the minimum peptide necessary for the interaction of side-chain COO−of Glu at the 12th position with Ca2+ in the bidentate coordination mode. We discuss the relationship between the amino acid length of synthetic peptide analogues and the formation of Ca2+-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