Table 1.
Mitochondrial ion channels
| Location | Type | Conductance (∼150 mM salt) | Modulators/Inhibitors | Putative Role |
|---|---|---|---|---|
| Outer membrane | VDAC (porin) | 0.5–4 nS | Bax/Bak/Bcl-xL, TOM20, Ca2+, pH, ΔV, NADH, VDAC modulator | Metabolic transport, cytochrome C release/apoptosis, PTP complex |
| TOM40 (PSC) | 0.5 nS | Signal peptides | Protein transport | |
| BH proteins | — | Bax/Bid/Bik | Cytochrome C release/apoptosis | |
| Misc. | 10–307 pS | ΔV (for > 100 pS) | — | |
| Inner membrane | Ca2+ uniporter | — | Divalents, nucleotides | Ca2+ uptake |
| PTP MCC | 0.03–1.5 nS | Ca2+, ΔV, signal peptides, CsA | Protein transport | |
| PTP MMC | 0.3–1.3 nS | CsA, pH, Ca2+, thiols, Bax, ANT inhibition | Necrosis, apoptosis | |
| UCP | 75 pS | Fatty acids | Thermogenesis | |
| KCa | 295 pS | Ca2+, ΔV, ChTx | Volume regulation | |
| KATP | 9.7 pS | ATP, GTP, palmitoyl-CoA, Mg2+, Ca2+ | Volume regulation, protection, apoptosis | |
| IMACs | 45, 450 pS | ATP | (In yeast) volume regulation | |
| 15 pS (LCC) 107 pS (centum pS) | Mg2+, pH, P1, thiols, DIDS, Cationic amphiphiles | Volume regulation |
A summary of mitochondrial ion channel types identified either in isolated mitochondria, proteolipid bilayers, or in patch-clamp experiments. Detected single channel conductances have been tentatively assigned to a given type, but these assignments have not been unequivocally proven. Abbreviations as follows: VDAC (porin), voltage-dependent anion channel; TOM40 (PSC), TOM20, pore forming translocases in outer membrane; BH proteins, Bcl2 homology proteins; Misc., miscellaneous conductances reported by Moran et al. (1992); PTP, permeability transition pore; MCC, multiconductance channel; MMC, mitochondrial megachannel; UCP, uncoupling protein; IMAC inner membrane anion channel; LCC, low conductance channel; Bax, Bak, Bid, Bik, Bcl-xl, apoptosis-related proteins; ΔV, change in membrane voltage; CsA, cyclosporin A; ANT inhibition, adenine nucleotide translocase inhibition; ChTx, charybdotoxin; palmitoyl CoA, palmitoyl coenzyme A; P1, inorganic phosphate; thiols, redox-sensitive reactive thiols.