Coordination to divalent cations by calcium-binding proteins studied by FTIR spectroscopy

We review the Fourier-transform infrared (FTIR) spectroscopy of side-chain COO− groups of Ca2 +-binding proteins: parvalbumins, bovine calmodulin, akazara scallop troponin C and related calcium binding proteins and peptide analogues. The COO− stretching vibration modes can be used to identify the coordination modes of COO− groups of Ca2 +-binding proteins to metal ions: bidentate, unidentate, and pseudo-bridging. FTIR spectroscopy demonstrates that the coordination structure of Mg2 + is distinctly different from that of Ca2 + in the Ca2 +-binding site in solution. The interpretation of COO− stretches is ensured on the basis of the spectra of calcium-binding peptide analogues. The implication of COO− stretches is discussed for Ca2 +-binding proteins. This article is part of a Special Issue entitled: FTIR in membrane proteins and peptide studies.

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► We review the FTIR spectroscopy of side-chain COO− groups of Ca2 +-binding proteins.
► The coordination structure of Mg2 + is different from that of Ca2 +.
► The downshift of the COO− antisymmetric stretch is a commonly observed feature.
► FTIR identifies the amino acid residues involved in coordination to metals.