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

Abstract

Proton and 31P NMR experiments were employed in the study of the weak stoichiometric 1:1 complex that is formed between CoA and Mn(II). The distances in solution between the 3 P atoms and the Mn(II) ion were obtained at 287 and 298 K over a pH range of 6.3-7.7. The correlation time .tau.c 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 [reciprocal of the inner sphere relaxation rate] value-obtained for the water protons for solutions where most of the Mn(II) ions are complexed. Paramagnetic spin-lattice relaxation rates for all 3 P atoms in the CoA molecule were obtained using proton decoupled Fourier transform 31P NMR techniques. For most probable values of 2 or 3 water molecules in the CoA-Mn(II) complex, the distances between the Mn(II) ion and the 3 P nuclei are 4.0 .+-. 0.4 .ANG. (1 .ANG. = 0.1 nm) or 3.7 .+-. 0.4 .ANG., 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 O of the 3 phosphate groups in the CoA-Mn(II) complex.