Mg2+ binding to coenzyme A

Abstract

Magnesium (Mg 2+ ), the second most abundant intracellular cation, plays a crucial role in cellular functions. Inthis study, we investigate the interaction between Mg 2+ and coenzyme A (CoA), a thiol-containing cofactor cen-tral to cellular metabolism also involved in protein modifications. Isothermal titration calorimetry revealed a 1:1binding stoichiometry between Mg 2+ and free CoA under biologically relevant conditions. Association constantsof (537 ± 20) M −1 and (312 ± 7) M −1 were determined at 25 °C and pH 7.2 and 7.8, respectively, suggestingthat a significant fraction of CoA is likely bound to Mg 2+ both in the cytosol and in the mitochondrial matrix. Ad-ditionally, the process is entropically-driven, and our results support that the origin of the entropy gain is sol-vent-related. On the other hand, the combination of 1- and 2-dimensional nuclear magnetic resonance spec-troscopy with molecular dynamics simulations and unsupervised learning demonstrate a direct coordination be-tween Mg 2+ and the phosphate groups of the 4-phosphopantothenate unit and bound to position 5’ of the adeno-sine ring. Interestingly, the phosphate in position 3′ only indirectly contributes to Mg 2+ coordination. Finally, wediscuss how the binding of Mg 2+ to CoA perturbates the chemical environment of different CoA atoms, regard-less of their apparent proximity to the coordination site, through the modulation of the CoA conformational land-scape. This insight holds implications for understanding the impact on both CoA and Mg 2+ functions in physio-logical and pathological processes.