Identification of a crab gill FXYD2 protein and regulation of crab microsomal Na,K-ATPase activity by mammalian FXYD2 peptide

► This work describes the first evidence of the occurrence of an FXYD in invertebrates. ► This FXYD can be phosphorylated by endogenous PKA. ► The mammalian FXYD2 (from pig kidney) readily regulates the C. danae Na,K-ATPase. ► FXYD increased the Vmax of the ATP hydrolysis and the NH4+ affinity of C. danae ATPase. ► C. danae enzyme activation was sensitive to PKA phosphorylation of the mammalian FXYD2.