Purification and Patch Clamp Analysis of Two Mitochondrial Channels
Patch clamping has revealed the presence in mitochondrial membranes of several channel types, of conductance ranging from 6 pS to 1.3 nS in the presence of 150 mM KC1 or NaCl. A voltage-gated channel of about 107 pS conductance has been found in patches of mitoplasts and artificial membranes incorporating mitochondrial membrane fragments or fractions (Sorgato et al., 1987 & 1989; Kinnally et al. 1989; Moran et al., 1990; Klitsch & Siemen, 1991; Inoue et al, 1991). An ATP-sensitive K+ channel of 10 pS conductance in the presence of 100 mM KCl has been seen in patches of mitochondrial inner membrane (Inoue et al., 1991). A 1.3 nS mega-channel, which is opened by mM levels of Ca++ and blocked by cyclosporin A (Petronilli et al., 1989; Szabó & Zoratti, 1991 & 1992), appears to mediate the permeability transition associated with Ca++ loading (Broekemeier et al., 1989). An apparently equivalent multiconductance channel (MCC) exhibiting transitions ranging from 30 pS to 5 nS is found to be activated by Ca++ or high voltage (Kinnally et al., 1991, 1992; Antonenko et al., 1991; Zorov et al., 1992). A water-soluble 60 kDa protein extracted from mitochondria in ethanol was earlier reported to induce variable conductance increments in black lipid membranes (Mironova, 1981).
KeywordsPermeability Glycerol EDTA Sedimentation Electrophoresis
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