Changes in properties of the inner mitochondrial membrane during mitochondrial biogenesis in aging sweet potato tissue slices in relation to the development of cyanide-insensitive respiration.

Protein and phospholipid of the inner mitochondrial membrane in sweet potato root tissue increased after a lag phase during aging of the sliced tissue. The protein, but not the phospholipid, from aged slices was more insoluble in a solution containing sodium deoxycholate and sodium cholate than that from fresh tissue. There were differences in polypeptide composition between deoxycholate-cholate-soluble and -insoluble fractions as determined by polyacrylamide-gel electorophoresis of membrane fragments in the presence of sodium dodecyl sulfate. However, no difference was observed between mitochondrial membranes from fresh and aged slices. When disrupted mitochondrial membrane was subjected to equilibrium density centrifugation, two bands were obtained from aged slices but only one band from fresh tissue. The lighter band from aged slices was indentical to the single band from fresh tissue. The denser band was very poor in phospholipid, and the protein was very insoluble in deoxycholate-cholate solution. The denser membrane fragments possessed a cyanide-insensitive respiratory chain whereas the lighter did not. It is proposed that the development of the cyanide-insensitive respiration in aging slices is related to the formation of phospholipid-deficient mitochondrial membrane.