PMID:6257692
| Citation |
Markham, GD (1981) Spatial proximity of two divalent metal ions at the active site of S-adenosylmethionine synthetase. J. Biol. Chem. 256:1903-9 |
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| Abstract |
S-Adenosylmethionine synthetase from Escherichia coli is shown to require 2 divalent metal ions/enzyme subunit for maximal enzymatic activity. In the absence of substrate, the tetrameric enzyme binds 1 Mn(II) ion/subunit, whereas in the presence of a nucleotide substrate, adenylylimidodiphosphate, or the product pyrophosphate, there are two Mn(II)-binding sites/subunit. Electron paramagnetic resonance spectra of Mn(II) bound to the enzyme reveal a spin exchange interaction between 2 Mn(II) ions in complexes of enzyme and Mn(II) which also contain adenosylmethionine, K+, and either pyrophosphate or imidotriphosphate. Since a spin exchange interaction requires orbital overlap between the 2 ions, the metal ions must be bound close to one another, and they may share a common ligand. |
| Links | |
| Keywords |
Adenylyl Imidodiphosphate; Binding Sites; Electron Spin Resonance Spectroscopy; Escherichia coli/enzymology; Kinetics; Manganese/pharmacology; Methionine Adenosyltransferase/metabolism; Protein Binding; Protein Conformation; Transferases/metabolism |
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