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Updated: Aug 19, 2026

Characterization of Membrane Transporters by Heterologous Expression in E. coli and Production of Membrane Vesicles
Published on: December 31, 2019
Bidirectional transport of spermine in rat liver mitochondria
D Siliprandi1, A Toninello, L Dalla Via
1Dipartimento di Chimica Biologica Universita' di Padova, Italy.
Abstract:
Further study of the mitochondrial transport of spermine (Toninello et al. (1988) J. Biol. Chem. 263, 19407) shows that, after loading rat liver mitochondria with [14C]spermine and [32P]phosphate, these components are released together into the surrounding medium by adding mersalyl or N-ethylmaleimide. On later addition of dithioerythritol, both are recaptured, but if acetate or nigericin are added instead, only spermine re-enters and there is continued export of phosphate. This bidirectional transport of spermine in and out mitochondria is driven, respectively, by membrane potential and pH gradient at constant protonmotive force. Results using [14C]spermine or [32P]phosphate, in conjunction with the their unlabelled isomers and with or without carbonyl cyanide/p-trifuloromethoxyphenylhydrazone (FCCP) present suggest that there is a continuous energy-dependent efflux-influx cycling of spermine and phosphate.
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