[Permeability of yeast mitochondrial internal membrane: structure-activity relationship].

In order to investigate the possible relations between the anionic permeability and the functions (or the structure ) of the inner mitochondrial membrane, three types of organelles isolated from S. cerevisiae were tested: mitochondria (aerobic culture), promitochondria (anaerobic culture) and CAP-mitochondria (aerobic culture with chloramphenicol added). By using the technique of swelling in isoosmotic potassium salts, after a derermination of the isotonic conditions, it was possible to discriminate between an electrogenic (valinomycin induced) or an electroneutral (both valinomycin and uncoupler induced) translocation. 1) Mitochondria: The permeability properties of mitochondria are energy dependent: a) Respiring mitochondria are permeable to Cl-; Mg2+, however, inhibits this translocation. Phosphate transport seems to be exclusively electrogenic and mersalyl sensitive, but swelling inhibition by that thiol reagent is restored by Mg2+. b) Non respiring mitochondria are impermeable to Cl-, but ATP addition restores the permeability. Thiocyanate permeates as the anionic form and acetate as the undissociated form. The phosphate transport, sensitive to mersalyl, seems to be partially electrogenic. 2) Promitochondria: Deficient of respiratory enzymes but containing an oligomycin sensitive ATPase, they are impermeable to Cl- only when Mg2+ is added. In these conditions, an electrogenic phosphate transport, sensitive to mersalyl, is observed. 3) CAP-mitochondria: Although CAP-mitochondria are cytochrome deficient and contain an oligomycin insensitive ATPase, they are also impermeable to Cl- in presence of Mg2+. As in fully differenciated mitochondria, an electroneutral phosphate entry is observed; Mg2+ is required for mersalyl sensitivity.