Calcium-Dependent Nonspecific Permeability of the Inner Mitochondrial Membrane Is Not Induced in Mitochondria of the Yeast Endomyces magnusii

Y. I. Deryabina, E. P. Isakova, E. I. Shurubor, and R. A. Zvyagilskaya^*

Bach Institute of Biochemistry, Russian Academy of Sciences, Leninsky pr. 33, Moscow 119071, Russia; fax: (7-095) 954-2732; E-mail: renata_z@inbi.ras.ru

^* To whom correspondence should be addressed.

Received February 12, 2004; Revision received March 30, 2004

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Mitochondria of the yeast Endomyces magnusii were examined for the presence of a Ca²⁺- and phosphate-induced permeability of the inner mitochondrial membrane (pore). For this purpose, coupled mitochondria were incubated under conditions known to induce the permeability transition pore in animal mitochondria, i.e., in the presence of high concentrations of Ca²⁺ and P_i, prooxidants (t-butylhydroperoxide), oxaloacetate, atractyloside (an inhibitor of ADP/ATP translocator), SH-reagents, by depletion of adenine nucleotide pools, and deenergization of the mitochondria. Large amplitude swelling, collapse of the membrane potential, and efflux of the accumulated Ca²⁺ were used as parameters for demonstrating pore induction. E. magnusii mitochondria were highly resistant to the above-mentioned substances. Deenergization of mitochondria or depletion of adenine nucleotide pools have no effect on low-amplitude swelling or the other parameters. Cyclosporin A, a specific inhibitor of the nonspecific permeability transition in animal mitochondria, did not affect the parameters measured. It is thus evident that E. magnusii mitochondria lack a functional Ca²⁺-dependent pore, or possess a pore differently regulated as compared to that of mammalian mitochondria.

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KEY WORDS: mitochondria, Endomyces magnusii, membrane potential, Ca²⁺-transport, Ca²⁺-induced nonspecific permeability

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