A Phosphorus‐Magnetic‐Resonance Study of the Interaction of Mg2+ with Adenyl‐5′‐yl Imidodiphosphate

Abstract
The interaction of Mg2+ with adenyl-5''-yl imidodiphosphate, AMP-P(NH)P, was studied at basic and acidic pH values by 31P-NMR spectroscopy in aqueous solution. The results suggest that Mg2+ binds simultaneously to 1 (or both) of the 2 free O atoms of the .beta.-phosphate moiety and to the N atom of the phosphate chain (P.alpha.-O-P.beta.-N-P.gamma.). The interaction arises from 1:1 complexing of Mg2+ to AMP-P(NH)P. The mode of the Mg2+ binding on the phosphate chain remains the same at basic and acidic pH values. As in the case of ATP and ADP, the association of Mg2+ reduces the pK by about 1.5 units. P titration curves showed that when the phosphate chain does not possess the regular periodicity (O-P.alpha.-O-P.beta.-X-P.gamma.-O,X .noteq. O) as in the case of ATP, protonation of the terminal phosphate group may induce a 31P chemical shift variation less important for this group than for the preceding one.

This publication has 22 references indexed in Scilit: