Soluble P‐type ATPase from an archaeon, Methanococcus jannaschii

Abstract
MJ0968 has been proposed to be an ancestor of P‐type ATPase, because its primary structure is highly homologous to that of the core catalytic domain of P‐type ATPase. However it completely lacks amino acid sequences that possibly constitute transmembrane domains. To examine if MJ0968 is indeed a P‐type ATPase, it was overexpressed in Escherichia coli and purified. It did show ATPase activity, autophosphorylation and inhibition by vanadate. All these properties support the idea that MJ0968 is indeed a soluble P‐type ATPase.