The 40,000-dalton glycoprotein and 2000-dalton peptide inducing selective Ca2+-transport through bilayer lipid membranes were isolated from beef heart homogenate and mitochondria. Micromolar concentrations of these substances were found to increase the conductivity of membranes by 3-4 orders. Trans-membrane Ca2+ gradient induces an electric potential difference whose magnitude is close to the theoretical for ideal Ca2+ selectivity. The inhibitor of mitochondrial Ca2+ transport, ruthenium red, abolishes both the glycoprotein- and peptide-induced Ca2+ transport in bilayer lipid membranes. Thiol groups essential for Ca2+ transport activity were revealed in the glycoprotein and peptide. Addition of these substances to rat liver mitochondria induces Ca2+-dependent inhibition of the state 3 respiration that can be released by uncouplers (oligomycin-like effect).

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In mitoplasts, respiratory stimulation by ADP, palmitate, DNP and CCCP and sensitivity of respiration to carboxyatractylate are considerably less pronounced than in mitochondria. Addition of porin-containing preparations (purified outer membranes or solubiiized mitochondrial porin) to mitoplasts results in partial restoration of the oxygen consumption and sensitivity to carboxyatractylate (CAT). The uncoupling effect of FCCP in mitoplasts is CAT-resistant and does not depend on added porin. It is suggested that mitochondrial porin may be a natural activator of ADP/ATP antiporter and succinate carrier in mitochondria.

Benzopyryhumdye BDBP was found to be an effective uncoupler of oxidative phosphorylation It stimulates state 4 respiration of mitochondria 2-fold at about 2 PM, reveals a maximum stimulation (&fold) at 30 PM and inhibits the respiration at htgher concentrattons. BDBP is also an effecttve proton (hydroxyl) carrier through bilayer lipid membranes (BLM) as ts seen from the electrtcal properties of BLM with BDBP. Picrate enhances the effects of BDBP on the mttochondnal resptratton and BLM conductance. The BDBP activtttes arc accounted for by formation of dimers and complexes with ptcrate.

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