Biochemical studies on the developing thoracic muscles of the tobacco horn worm. I. Amino acid incorporation into mitochondria.

Mitochondrial fractions isolated from thoracic muscles of the tobacco horn worm larvae and moths, free of bacterial contaminations, incorporate amino acids into proteins. Optimum activity requires the presence of ATP, an ATPgenerating system, and an amino acid mixture. The pH optimum is around 7.2. The system is not affected by cycloheximide, ribonuclease, or actinomycin D. Puromycin completely inhibits the incorporation, while D-chloramphenico1 reduces the activity by over 50%. The incorporation activity is under physiological control. Mitochondrial fractions from pupae of intermediate developmental stages show the highest activity, while the fractions from the young pupae and from the adult moths exhibit much lower activities.