Cytoplasmic and mitochondrial arginine kinases in Drosophila: evidence for a single gene

Mitochondrial and cytoplasmic isozymes of arginine kinase have been identified in Drosophila melanogaster. On the basis of their immunological similarity, parallel dosage responses, and cosegregation of electrophoretic mobility differences, it is concluded that both isozymes are the product of a single gene. The consequences of this in relation to the regulation and evolution of this unusual gene-enzyme system are discussed. It is inferred that the origin of the phosphagen shuttle must predate the divergence of invertebrates and vertebrates.