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. FUR 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. (C) 2012 Elsevier B.V. All rights reserved.