Localization of arginine kinase in muscles fibres of Drosophila melanogaster.

Arginine kinase (AK), a monomeric protein of mol. wt. 40 000, was purified from adult Drosophila melanogaster. Antiserum to AK was raised in rabbits; its specificity was established by immunodiffusion tests and by immunoreplicas of electropherograms. After electrophoresis in non-denaturing conditions, the immunoreactive material was shown to possess enzymatic activity. Localization of AK by indirect immunofluorescence on washed myofibrils showed that at least a fraction of the total cellular AK is bound to the contractile apparatus. In muscle fibres of third instar larvae and in isolated adult fibrillar flight muscle myofibrils, AK was localized within the Z-line region. Adult tubular muscle fibres (tergal depressor of the trochanter) showed fluorescence in the A-band. In all cases, the localization was independent of the state of contraction. Vertebrate B- and M-type creatine kinases have previously been localized at the Z-line and A-band (M-line) regions, respectively. Isoenzymic forms of AK have not been detected in Drosophila, however.