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).
KeywordsMitochondrial Membrane Single Channel Conductance Single Channel Current Submitochondrial Particle Black Lipid Membrane
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