Molecular bases of circadian magnesium rhythms across eukaryotes

Circadian clocks allow for the physiological anticipation of daily environmental changes. A circadian rhythm in intracellular Mg²⁺ was recently discovered in multiple eukaryotes. Given the pivotal role for Mg²⁺ in metabolism, Mg²⁺ rhythms could affect cellular energy expenditure over the daily cycle. To probe the potential mechanisms underlying the generation of cellular Mg²⁺ rhythms, we present a phylogenetic analysis of Mg²⁺ transport proteins. Extensive conservation was observed for ancestral prokaryotic proteins, identifying these as candidate proteins mediating Mg²⁺ rhythms across eukaryotes. We also posit that shared allosteric regulation of Mg²⁺ transport proteins might underlie Mg²⁺ rhythms and propose a reciprocal feedback model between the rhythmic usage of Mg²⁺ and rhythmic transport activity.