A magnetic resonance study of the coenzyme A – manganese(II) complex in solution

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Abstract
Proton and 31P magnetic resonance experiments were employed in the study of the weak, stoichiometric, one-to-one complex that is formed between coenzyme A and manganese-(II). The distances in solution between the three phosphorus atoms and the manganese(II) ion are obtained at 287 K and at 298 K. The experiments are carried out over a pH range of 6.3 to 7.7. The correlation time τc of the water molecules bound to the Mn(II) ion in the CoA–Mn(II) complex was calculated using the Solomon–Bloembergen equation from the T1M value obtained for the water protons for solutions where most of the Mn(II) ions are complexed. Paramagnetic spin-lattice relaxation rates for all three phosphorus atoms in the CoA molecule were obtained using proton decoupled Fourier transform 31P nmr techniques. For most probable values of two or three water molecules in the CoA–Mn(II) complex, the distances between the manganese (II) ion and the three phosphorus nuclei are 4.0 ± 0.4 Å (1 Å = 0.1 nm) or 3.7 ± 0.4 Å respectively for 0.062 M CoA solutions. For experiments carried out on 0.010 M CoA, a correlation time which has been determined previously for propionyl CoA was used for the distance calculations and the distances remain unchanged within experimental error. These results indicate that the Mn(II) ion coordinates equally with the oxygens of the three phosphate groups in the CoA–Mn(II) complex.