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Mitochondrial anion carriers

Tire uncoupling protein resembles the ATP/ADP and phosphate anion carriers (Table 18-8), 1 which all have similar sizes and function as homodimers. Each monomeric subunit has a triply repeated 100-residue sequence, each repeat forming two transmembrane helices. Most mitochondrial transporters carry anions, and UCP1 will transport Cl. h/1 However, the relationship of chloride transport to its real function is unclear. Does the protein transport H+... [Pg.1048]

Mujahid A., Y. Akiba, C.H. Warden and M. Toyomizu, 2007. Sequential changes in superoxide production, anion carriers and substrate oxidation in skeletal muscle mitochondria of heat-stressed chickens. FEES Lett. 581, 3461-3467. Mujahid A., Y. Akiba and M. Toyomizu, 2009. Olive oil-supplemented diet alleviates acute heat stress-induced mitochondrial ROS production in chicken skeletal muscle. Am. J. Physiol. Regul. Comp. Physiol. 297, R690-698. [Pg.70]

Now, we may consider in detail the mechanism of oxygen radical production by mitochondria. There are definite thermodynamic conditions, which regulate one-electron transfer from the electron carriers of mitochondrial respiratory chain to dioxygen these components must have the one-electron reduction potentials more negative than that of dioxygen Eq( 02 /02]) = —0.16 V. As the reduction potentials of components of respiratory chain are changed from 0.320 to +0.380 V, it is obvious that various sources of superoxide production may exist in mitochondria. As already noted earlier, the two main sources of superoxide are present in Complexes I and III of the respiratory chain in both of them, the role of ubiquinone seems to be dominant. Although superoxide may be formed by the one-electron oxidation of ubisemiquinone radical anion (Reaction (1)) [10,22] or even neutral semiquinone radical [9], the efficiency of these ways of superoxide formation in mitochondria is doubtful. [Pg.750]

McEnery, M.W., Snowman, A.M., Trifiletti, R.R., and Snyder, S.H., 1992, Isolation ofthe mitochondrial benzodiazepine receptor association with the voltage-dependent anion channel and the adenine nucleotide carrier, Proc.Natl.Acad.Sci. U.S.A. 89 3170-3174. [Pg.186]

The idea of using organotin compounds as ionophores was based on the fact that since, like carbon, tin forms covalent bonds via sp hybridization, and with the presence of empty d orbitals, it can coordinate with up to three extra electron-donating substituents, such as Lewis-basic anions. It was Selwyn, in 1970,9.10 ujal (ook advantage of this property and showed clearly the direct role of the trimethyltin, tri-n-propyltin, tri-n-butyltin, and triphenyltin chlorides on the active chloride transport mediated in mitochondrial membranes, as shown in Figure 3.4.5. It was also shown in this study that the mediation is based on chloride-hydroxide antiporter transport. This fact was verified many years later, as Simon showed, based on NMR and other studies, that indeed these compounds act as neutral carriers in liquid polymeric membranes. ... [Pg.327]

On the addition of the electron from the second QH > molecule, this quinone radical anion takes up two protons from the matrix side to form Q.H i. The removal of these two protons from the matrix contributes to the for-matiun of the proton gradient. In sum, four protons are released on the cytoplasmic side, and two protons are removed from the mitochondrial matrix In one Q cycle, two QH molecules are oxidized to form two Q molecules, and then one Q molecule is reduced to QH >. Why this complexity The formidable problem solved here is to efficiently funnel electrons from a two-electron carrier (QHt) to a one-electron carrier (cytochrome c). 1 he cytochrome h component of the reductase is in essence a recycling device that enables both electrons of QH to be used effectively. [Pg.514]

Fig. 16. Mitochondrial import of cholesterol. The StAR protein is the major cholesterol (CHOL) carrier bringing the lipid to import sites. The StAR protein is phosphorylated by cyclic AMP-dependent protein kinase (PKA) that is recruited to the mitochondria by the protein PAP7. PAP7 is a binding partner of the peripheral benzodiazepine receptor/translocator protein (TSPO), which forms a complex with the voltage-dependent anion channel (VDAC) and an adenine nucleotide transporter (ANT) at contact sites between the inner and outer mitochondrial membranes. The multiprotein complex constitutes a cholesterol transporter that moves cholesterol from StAR to the inner mitochondrial membrane where the side-chain cleavage enzyme (CYP-11 Al) converts it to pregnenolone (PREG). Fig. 16. Mitochondrial import of cholesterol. The StAR protein is the major cholesterol (CHOL) carrier bringing the lipid to import sites. The StAR protein is phosphorylated by cyclic AMP-dependent protein kinase (PKA) that is recruited to the mitochondria by the protein PAP7. PAP7 is a binding partner of the peripheral benzodiazepine receptor/translocator protein (TSPO), which forms a complex with the voltage-dependent anion channel (VDAC) and an adenine nucleotide transporter (ANT) at contact sites between the inner and outer mitochondrial membranes. The multiprotein complex constitutes a cholesterol transporter that moves cholesterol from StAR to the inner mitochondrial membrane where the side-chain cleavage enzyme (CYP-11 Al) converts it to pregnenolone (PREG).
Fig. 11 Anionic uncoupiers increase mitochondrial respiration, but decrease ATP formation. Anionic uncoupiers, such as drugs with a carboxylic group (R-COOH) can translocate protons across the inner membrane, and may then dissociate into a proton (H ) and the anionic form (R-COO ) in the more alkaline matrix. The negatively charged R-COO is then pushed back through diverse inner membrane carriers (IMCs) into the inteimembrane space by the mitochondrial membrane potential (A /m), ready for another cycle of proton translocation. The reentry of protons into the mitochondrial matrix decreases the thus unleashing the flow of electrons in the respiratory chain and increasing mitochondrial respiration. However, ATP synthase is bypassed, so that the increased respiration produces heat instead of ATP... Fig. 11 Anionic uncoupiers increase mitochondrial respiration, but decrease ATP formation. Anionic uncoupiers, such as drugs with a carboxylic group (R-COOH) can translocate protons across the inner membrane, and may then dissociate into a proton (H ) and the anionic form (R-COO ) in the more alkaline matrix. The negatively charged R-COO is then pushed back through diverse inner membrane carriers (IMCs) into the inteimembrane space by the mitochondrial membrane potential (A /m), ready for another cycle of proton translocation. The reentry of protons into the mitochondrial matrix decreases the thus unleashing the flow of electrons in the respiratory chain and increasing mitochondrial respiration. However, ATP synthase is bypassed, so that the increased respiration produces heat instead of ATP...
At least seven carriers control entry through the mitochondrial membrane. One carrier facilitates entry of succinate, D- and L-malate, malonate, and m o-tartrate anions, but not tartrate, maleate, or fumarate. Another mediates the entry of citrate, m-aconitate, wocitrate, and D- or L-tartrate, but not fumarate or maleate. A third carrier transports adenosine nucleotides. Also phosphate anions can enter mitochondria whereas other inorganic anions cannot (Chappell, 1966). [Pg.69]

The placement of the components of the respiratory chain in the inner mitochondrial membrane is of considerable importance to the mechanism of the chemiosmotic theory. Mitchell (1967) calls this the "coupling membrane" H+, citric-acid-cycle anions, amino acids, and cations can be transported across this membrane by specific carriers imbedded in it. The respiratory chain is folded into three "loops"... [Pg.501]

In a number of biosynthetic pathways, such as fatty acid synthesis and gluconeogenesis, the citric acid cycle provides key intermediates. Citric-acid-cycle anions such as malate and citrate move across the inner mitochondrial membrane into the cytosol by poorly understood translocation processes (Chappell and Haarhoff, 1967 Chappell, 1968). Figure 4 is a list of these anion translocators taken from an excellent review of anion transport by Williamson (1976) to which the reader is directed for a more detailed treatment of this subject. Most anion translocations from cytosol to mitochondria involve an exchange for anions moving in the opposite direction. It is presumed that this translocation process is carrier mediated, although specific carrier molecules have not been purified and characterized. The exchange-translocation processes can be grouped into three types. [Pg.506]


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See also in sourсe #XX -- [ Pg.201 ]




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Anion carriers

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