Differentiation between mitochondrial and cytoplasmic protein subunits of blowfly flight muscle mitochondria synthesized in vivo.

Total adult blowfly flight-muscle mitochondrial protein was labelled in vivo with [14C]leucine. The labelled proteins were enumerated and characterized by their electrophoretic mobility using sodium dodcecyl sulphate/polyacrylamide gel electrophoresis and autoradiography. When different gel concentrations were used to resolve the maximum number of bands and their molecular weights, it was possible to observe at least 35 electrophoretic bands after staining and scanning; their molecular weights ranged between 11 000 and 130 000. When mitochondria were labelled in the presence of cycloheximide, only 6--8 bands could be identified on gradient gels after electrophoresis and autoradiography. By comparison, controls (where cycloheximide was absent), which were run alongside the drug-treated mitochondria, revealed 17--20 radioactively labelled bands from densitometric tracings. Whilst the molecular weights of these bands could be estimated, it was difficult to identify the precise nature and function of the proteins made in these mitochondria.