A new functional role of potassium

Metal ions play vital roles in numerous biological processes, including energy generation, neuro‐transmission, signal transduction, transportation of nutrients, and maintenance of pH and osmolarity. To gain better insights into metal metabolism and metalloprotein biosynthesis, we have searched new genes involved in copper and iron utilization. A predicted potassium‐proton antiporter was identified as a new molecular factor necessary for biosynthesis of functional ferroxidases at the secretory pathway. Copper serves as a cofactor of ferroxidases in various organisms, including humans. Both copper and iron are required for respiratory chain electron transport and many other vital biochemical processes; however, the implication of potassium in copper and iron metabolism is an unanticipated discovery. Several lines of our study indicate that potassium transported into the secretory pathway is required for copper metallation of ferroxidases during their biosynthesis. This new discovery has opened avenues by which we can gain better insights into the mechanisms underlying biosynthesis of cuproproteins and potentially other metalloproteins. This study characterizes a new molecular factor involved in the metabolism of vital metal ions, copper, iron and potassium and discovers a novel functional role of a major intracellular cation potassium.