LAUSR

A broad range of biochemicals, from proteins to nucleic acids, function properly only when associated with a metal, usually a divalent cation. Not any divalent metal will do: these metals differ in their ionic radius, dissociation in water, ionization potential, and number of unpaired electrons in their outer shells, and so substituting one metal for another often changes substrate positioning, redox reactivities, and physiological performance, and thus may serve as a regulatory mechanism. For instance, exchanging manganese for magnesium in several chloroplast enzymes maintains plant carbon-nitrogen balance under rising atmospheric CO2 concentrations. Here, we review this and a few other cases where association of proteins or nucleic acids with different metals control metabolism.