title: Fourier-transform infrared spectroscopic studies on the coordination of the side-chain COO- groups to Ca2+ in equine lysozyme.
abstract: Interactions between Ca2+ and the Asp side chains in the Ca2+-binding site of equine lysozyme were investigated by Fourier-transform infrared (FT-IR) spectroscopy. In the spectrum of equine lysozyme, the intensities of the bands at about 1595 cm-1 and 1578 cm-1 in the region of the COO antisymmetric stretches increased upon Ca2+ binding. In the region of the COO- symmetric stretches, the loss of intensity at about 1388 cm-1 and gains of intensities at about 1423 cm-1 and 1403 cm-1 were observed due to Ca2+ binding to equine lysozyme. The spectral changes for equine lysozyme indicate that the COO- groups of Asp85, Asp90 and Asp91 in the Ca2+-binding site coordinate to Ca2+ in the pseudo-bridging mode, where divalent metal cation is bound to one of the two oxygens in the COO- group and a water molecule is hydrogen bonded to the other oxygen. The results presented here provide further evidence for a high degree of similarity between Ca2+-binding lysozyme and alpha-lactalbumin. The effects of Ca2+ binding on the main-chain conformation of equine lysozyme were compared with those of bovine alpha-lactalbumin and hen egg-white lysozyme.
authors.affiliation: Division of Biological Sciences, Graduate School of Science, Hokkaido University, Sapporo, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Mizuguchi
authors.forename: M
authors.initials: M
authors.lastname: Nara
authors.forename: Y
authors.initials: Y
authors.lastname: Ke
authors.forename: K
authors.initials: K
authors.lastname: Kawano
authors.forename: T
authors.initials: T
authors.lastname: Hiraoki
authors.forename: K
authors.initials: K
authors.lastname: Nitta
mesh_terms: D000818:Animals; D001665:Binding Sites; D002118:Calcium / Q000737:chemistry* / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000737:chemistry; D002417:Cattle; D004529:Egg White; D006736:Horses; D006860:Hydrogen Bonding; D007768:Lactalbumin / Q000737:chemistry / Q000378:metabolism; D009113:Muramidase / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D013053:Spectrophotometry; D017550:Spectroscopy, Fourier Transform Infrared; D014867:Water / Q000737:chemistry / Q000378:metabolism
chemical_list: D002135:Calcium-Binding Proteins; D014867:Water; D007768:Lactalbumin; D009113:Muramidase; D002118:Calcium