title: Metal ion binding in triclinic lysozyme.
abstract: The binding sites of Mn2+, Co2+, and Gd3+ have been determined in triclinic lysozyme at pH 4.5 to 4.6. Mn2+ and Co2+ bind a site approximately 2.5 A from 1 of the oxygen atoms of the Glu-35 chain. The occupancy of the Mn2+ site is 0.22, corresponding to 1 bound ion for each 4.6 protein molecules. The occupancy of the Co2+ site is much lower, about 0.048. Gd3+ appears to be bound at two sites, the main one 2.5 A from an oxygen atom of the Glu-35 side chain, the other 3.1 A from an oxygen atom of the Asp-52 chain. The occupancy of both Gd3+ sites is low, 0.036 and 0.016, the latter being so low that the presence of the ion at this site is in doubt. The binding site of Mn2+ in the di(N-acetylglucosamine)-lysozyme complex has also been determined. It does not differ significantly from the Mn2+ binding site in the native protein, but the occupancy is lower, 0.16.
mesh_terms: D000117:Acetylglucosamine; D001665:Binding Sites; D003035:Cobalt; D005583:Fourier Analysis; D005682:Gadolinium; D006863:Hydrogen-Ion Concentration; D008345:Manganese; D008958:Models, Molecular; D009113:Muramidase; D010100:Oxygen; D011485:Protein Binding; D011487:Protein Conformation
chemical_list: D003035:Cobalt; D008345:Manganese; D005682:Gadolinium; D009113:Muramidase; D010100:Oxygen; D000117:Acetylglucosamine