Monovalent carboxylic ionophores inhibit transport of carbomoyl‐phosphate synthetase I into mitochondria in Reuber hepatoma H‐35 cells and cause accumulation of enzyme precursor

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Abstract
Transport of the precursor for carbamoyl‐phosphate synthetase I into mitochondria in Reuber hepatoma H‐35 cells was inhibited by adding monensin or nigericin to the culture medium at a concentration of 0.5 μM, and the enzyme precursor accumulated, mainly in the cytosolic fraction. Accumulated precursor was degraded slowly with a half‐life of more than 16 min. Valinomycin, nonactin, A23187, X‐537A (lasalocid), bromo‐lasalocid, and carbonyl cyanide m‐chlorophenylhydrazone did not exhibit these effects at concentrations at which they did not inhibit protein synthesis of the cells.