Investigations on the mitochondria of the housefly, Musca domestica L. III. Requirements for oxidative phosphorylation

Mitochondria in the flight muscles of insects. III. Mitochondrial cytochrome c in relation to the aging and wing beat frequency of flies

1. In the present study a correlation has been sought between aging, flight muscle mitochrondria (sarcosomes), cytochrome c, and flight ability in the blowfly, Phormia regina. 2. During the 1st week of adult life, individual sarcosomes increase in mass from 2.7 x 10(-7) microg. dry weight at the time of emergence, to 8.5 x 10(-7) microg. by the 7th day. During this period of growth, the number of sarcosomes per fly (6.7 x 10(8)) remains constant. When mature, the sarcosomes account for 32.6 per cent of the total muscle dry weight, or close to 40 per cent on a wet weight basis. 3. It appears probable that the high content of flight muscle cytochromes is entirely localized in the sarcosomes. The cytochromes continue to be synthesized and increase in titer within the sarcosomes for 7 days after adult emergence. 4. As determined spectroscopically, the various cytochrome components at all times maintain a constant ratio both to one another and to the sarcosomal dry weight. This suggests the possibility that the cytochrome system may be synthesized as a single entity. 5. The wing-beat frequency of Drosophila funebris and Phormia varies with the age of these flies, being lowest at the time of emergence and maximum after the 6th day. 6. The relations between wing-beat frequency, respiration during flight, and sarcosomal cytochrome c content are discussed. On the basis of some likely assumptions it is calculated that the cytrochrome c turnover number is over 5,000, and that the cytochrome c turns over once for every two wing-beat cycles.

The effect of temperature on oxidative phosphorylation with insect flight muscle mitochondria

The effect of different temperatures on the biochemical activity and morphology of insect flight muscle mitochondria was examined. It was found that respiration and phosphorylation have the same thermal response at temperatures of 25 degrees C. and below. The energy of activation for both systems is approximately 12,300 calories. Oxidation and phosphorylation can be uncoupled effectively by temperature, for at temperatures above 25 degrees C. there is more rapid heat inactivation of phosphorylation. This is evident from reduced P/O values as well as from morphological deterioration in the mitochondrial population. The thermal response of both this sarcosomal enzyme system and the respiration in the living fly are quantitatively similar.