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Interactions between the iron protein, Kp2, of nitrogenase manganese ions, magnesium ions, and the nucleotides ATP or ADP, have been studied in aqueous solution by monitoring the water proton NMR relaxation rate enhancement caused by Mn2+. Binding of Mn2+ to a molecule of Kp2 occurs at four sites, indistinguishable within experimental error, having a Kd = 350 +/- 50 micron. The Mn2+ - Kp2 complex has a low characteristic enhancement (epsilonb = 6 +/- 0.5). All four sites can alternatively bind Mg2+, not necessarily with the same dissociation constant, but with a mean Kd = 1.7 +/- 0.3 mM. Ternary complexes with the configuration EMS or (formula: see text) are formed between Kp2, Mn2+ and nucleotide (ATP or ADP). The ternary complexes with Mg2+ in place of Mn2+ probably have the latter configuration. A novel treatment of enhancement data (a 'high metal' approximation) is given.
E O Bishop, and
M D Lambert, and
D Orchard, and
B E Smith
August 1982,
Biochimica et biophysica acta,
E O Bishop, and
M D Lambert, and
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B E Smith
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Biopolymers,
E O Bishop, and
M D Lambert, and
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B E Smith
September 1971,
Proceedings of the National Academy of Sciences of the United States of America,
E O Bishop, and
M D Lambert, and
D Orchard, and
B E Smith
July 1977,
Journal of the American Chemical Society,
E O Bishop, and
M D Lambert, and
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B E Smith
November 1992,
The Journal of biological chemistry,
E O Bishop, and
M D Lambert, and
D Orchard, and
B E Smith
January 1977,
Journal of the American Chemical Society,
E O Bishop, and
M D Lambert, and
D Orchard, and
B E Smith
March 1981,
The Journal of biological chemistry,
E O Bishop, and
M D Lambert, and
D Orchard, and
B E Smith
January 1982,
Biopolymers,
E O Bishop, and
M D Lambert, and
D Orchard, and
B E Smith
May 1992,
The Journal of biological chemistry,
E O Bishop, and
M D Lambert, and
D Orchard, and
B E Smith
September 1998,
The Biochemical journal,
