ARGININE KINASE IS HIGHLY EXPRESSED IN THE COMPOUND EYE OF THE HONEY-BEE, APIS-MELLIFERA

We have cloned and sequenced a 1.68-kb cDNA encoding arginine kinase i n the honey bee, Apis mellifera. The predicted protein shows a high le vel of identity to known arginine kinases in invertebrates and to othe r proteins belonging to the conserved family of ATP: guanidino phospho -transferases. The pattern of expression of arginine kinase has been i nvestigated for the first time in various tissues including the brain, antennae and compound eye. Our results show that three isoforms of ar ginine kinase, transcribed from a single gene, are expressed in a char acteristic pattern in major tissues of the honey bee. Arginine kinase mRNA is relatively abundant in the central nervous system and in the a ntennae. However, the highest level of expression, that is at least tw o to three times higher than in the brain, is found in the compound ey e of the bee. By contrast, the levels of mRNAs encoding another metabo lically important enzyme, alpha-glycerolphosphate dehydrogenase (alpha -GPDH), are low in the eye. These findings suggest that arginine kinas e is an important component of the energy releasing mechanism in the v isual system that has high and fluctuating energy demands. Furthermore , our results support the role of phosphagen kinases in energy transpo rt in polarised cells and are consistent with the role of arginine kin ase as an energy shuttle that delivers ATP generated by mitochondria t o high energy-requiring processes, such as massive membrane turnover a nd pigment regeneration in the retina. (C) 1998 Elsevier Science B.V. All rights reserved.