Jen Christian Skou discovery of the “Sodium Pump” in 1957 was a pioneering step in cellular energetics. In a human body this single enzyme accounts for two-third of body energy. Ubiquitous in cells of the animal kingdom, 40 years after the discovery Skou received the 1997 Nobel Prize. Note the magnesium is a cofactor cation in this application “charge conservation” in the energy balance. The diagram above is from the Roche Biochemical webpage at location “R” and coordinate “2” of the chart.
Reference: Skou, J.C. The influence of some cations on an adenosinetriphosphatase from peripheral nerve. Biochim. Biophys. Acta 23 (1957) 394–401.