The mechanism of phosphate permeation in purified bean mitochondria

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The permeability properties and mechanism of Pi transport were investigated in purified bean mitochondria. 1. Purified bean mitochondria are impermeable to small molecules and ions. However, Pi, arsenate, acetate and formate can enter the osmotically active space of bean mitochondria. 2. Nigericin or the association of valinomycin and FCCP cause mitochondrial swelling in isoosmotic potassium phosphate. 3. The SH-blocking reagents mersalyl, pHMB and NEM inhibit various mitochondrial functions dependent on the translocation of Pi and arsenate across the membrane. These include the respiration stimulated by ADP, Ca^<2+>+Pi, and K^++valinomycin+Pi; the swelling in ammonium phosphate medium and, in the presence of nigericin, in potassium phosphate medium; the energy-linked valinomycin-induced swelling and the subsequent ClCCP-induced shrinking. The uncoupler-stimulated respiration, as well as the other processes when acetate is substituted for Pi, are not influenced by SH reagents. 4. Mersalyl and pHMB cause complete inhibition at about 20 nmoles/mg protein, whereas, NFM is effective at about 1 μmole/mg protein. The inhibition by mersalyl and pHMB, but not that by NEM, is sigmoidal and reversed by 2-mercaptoethanol. Non-inhibitory amounts of mersalyl protect the Pi transport from irreversible inhibition by NEM. 5. We concluded that a carrier-mediated transport system for Pi is present in bean mitochondria, and that some of its properties are similar to the Pi carrier of animal mitochondria.
日本植物生理学会の論文

The mechanism of phosphate permeation in purified bean mitochondria

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