A phosphorus-magnetic-resonance study of the interaction of Mg2+ with adenyl-5'-yl imidodiphosphate. Binding sites of Mg2+ ion on the phosphate chain.
The interaction of Mg2+ ions with adenyl-5'-yl imidodiphosphate, AMP-P(NH)P, has been studied at basic and acidic pH values by phosphorus magnetic resonance spectroscopy in aqueous solution. The results suggest that Mg2+ binds simultaneously to one (or both) of the two free oxygen atoms of the beta-phosphate moiety and to the nitrogen 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 both 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. On the other hand phosphorus 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 not equal to 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.
D000255:Adenosine Triphosphate / Q000031:analogs & derivatives*; D000266:Adenylyl Imidodiphosphate / Q000378:metabolism*; D001665:Binding Sites; D055598:Chemical Phenomena; D002621:Chemistry; D006863:Hydrogen-Ion Concentration; D008274:Magnesium / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D013329:Structure-Activity Relationship
D000266:Adenylyl Imidodiphosphate; D000255:Adenosine Triphosphate; D008274:Magnesium