Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Translocase of the outer mitochondrial membrane

Becker L et al. (2005) Preprotein translocase of the outer mitochondrial membrane reconstituted Tom40 forms a characteristic TOM pore. J Mol Biol 353 1011-1020 Blobel G, Dobberstein (1975a) Transfer of proteins across membranes. I. Presence of proteolytically processed and unprocessed nascent immunoglobulin light chains on membrane-bound ribosomes of murine myeloma. J Cell Biol 67 835-851 Blobel G, Dobberstein (1975b) Transfer to proteins across membranes. II. Reconstitution of functional rough microsomes from heterologous components. J Cell Biol 67 852-862... [Pg.62]

Fig. 20.20. Model for the import of nuclear-encoded proteins into the mitochondrial matrix. The matrix preprotein with its positively charged N-terminal presequence is shown in blue. Abbreviations OM, outer mitochondrial membrane IMS, intramembrane space IM, inner mitochondrial membrane TOM, translocases of the outer mitochondrial membrane TIM, translocases of the inner mitochondrial membrane mthspTO, mitochondrial heat shock protein 70. Fig. 20.20. Model for the import of nuclear-encoded proteins into the mitochondrial matrix. The matrix preprotein with its positively charged N-terminal presequence is shown in blue. Abbreviations OM, outer mitochondrial membrane IMS, intramembrane space IM, inner mitochondrial membrane TOM, translocases of the outer mitochondrial membrane TIM, translocases of the inner mitochondrial membrane mthspTO, mitochondrial heat shock protein 70.
Fig-i Mitochondrial protein import machinery as defined in S. cerevisiae. TOM translo-case of the outer mitochondrial membrane SAM sorting and assembly machinery TIM translocase of the inner mitochondrial membrane MIA mitochondrial IMS import and assembly machine PAM presequence translocase associated motor IMP inner membrane protease MPP mitochondrial processing peptidase. The numbers on the individual Tom, Sam, Tim or Pam components represent their approximate molecular masses in kDa. See text for mechanistic details. Adopted from Dolezal et al. 2006... [Pg.26]

In muscle, most of the fatty acids undergoing beta oxidation are completely oxidized to C02 and water. In liver, however, there is another major fate for fatty acids this is the formation of ketone bodies, namely acetoacetate and b-hydroxybutyrate. The fatty acids must be transported into the mitochondrion for normal beta oxidation. This may be a limiting factor for beta oxidation in many tissues and ketone-body formation in the liver. The extramitochondrial fatty-acyl portion of fatty-acyl CoA can be transferred across the outer mitochondrial membrane to carnitine by carnitine palmitoyltransferase I (CPTI). This enzyme is located on the inner side of the outer mitochondrial membrane. The acylcarnitine is now located in mitochondrial intermembrane space. The fatty-acid portion of acylcarnitine is then transported across the inner mitochondrial membrane to coenzyme A to form fatty-acyl CoA in the mitochondrial matrix. This translocation is catalyzed by carnitine palmitoyltransferase II (CPTII Fig. 14.1), located on the inner side of the inner membrane. This later translocation is also facilitated by camitine-acylcamitine translocase, located in the inner mitochondrial membrane. The CPTI is inhibited by malonyl CoA, an intermediate of fatty-acid synthesis (see Chapter 15). This inhibition occurs in all tissues that oxidize fatty acids. The level of malonyl CoA varies among tissues and with various nutritional and hormonal conditions. The sensitivity of CPTI to malonyl CoA also varies among tissues and with nutritional and hormonal conditions, even within a given tissue. Thus, fatty-acid oxidation may be controlled by the activity and relative inhibition of CPTI. [Pg.398]

Carnitine (p-hydroxy-y-trimethylammonium butyrate), (CHjljN"—CH2—CH(OH)—CH2—COO , is widely distributed and is particularly abundant in muscle. Long-chain acyl-CoA (or FFA) will not penetrate the inner membrane of mitochondria. However, carnitine palmitoyltransferase-I, present in the outer mitochondrial membrane, converts long-chain acyl-CoA to acylcarnitine, which is able to penetrate the inner membrane and gain access to the P-oxidation system of enzymes (Figure 22-1). Carnitine-acylcar-nitine translocase acts as an inner membrane exchange transporter. Acylcarnitine is transported in, coupled with the transport out of one molecule of carnitine. The acylcarnitine then reacts with CoA, cat-... [Pg.180]

FIGURE 31-7 Mitochondrial carriers. Ions and small molecules enter the intermembrane space, since the outer mitochondrial membrane is not a significant permeability barrier. However, the inner mitochondrial membrane is impermeable to ions except those for which there are specific carriers. Most of the carriers are reversible, as indicated by two-headed arrows. Compounds transported in one direction are indicated in red. The ATP/ADP translocase and the aspartate-glutamate carrier are both electrophoretic their transport is driven in the direction of the mitochondrial membrane potential, as indicated by red arrows. Glutamine is carried into the matrix by an electroneutral carrier. The unimpaired functioning of mitochondrial carriers is essential for normal metabolism. (Adapted with permission from reference [70].)... [Pg.547]

A nucleotide transporter (located in the outer mitochondrial membrane) that mediates one-for-one transloca-tion/exchange of cytosolic ADP for mitochondrial ATP. This translocase is potently inhibited by atractyloside and bonkregic acid. [Pg.33]

Carnitine acyltransferase I, which is located on the outer mitochondrial membrane, transfers the fatty acyl group from fatty acyl-CoA to the hydroxyl (OH) group of carnitine. The acyl-carnitine then moves across the intermembrane space to a translocase enzyme, which, in turn, moves the acyl-carnitine to carnitine acyltransferase II, which exchanges the carnitine for Coenzyme A. [Pg.11]

The mitochondrial permeability transition (MPT) is the loss of the inner mitochondrial membrane impermeability to solutes caused by opening of the MPT pore (MPTP). In turn, this action results in a loss of mitochondrial function and provides a common mechanism implicated in activation of mi-tophagy/autophagy, apoptosis, and necrosis in different cell systems. Although the composition of MPTP is not fully settled, multiple studies suggest involvement of adenine nucleotide translocase (ANT) in the inner mitochondrial membrane, voltage-dependent anion channel (VDAC or porin) in the outer membrane, and cyclophilin D (CypD) in the matrix. [Pg.179]

The molecular structure of the MPT pore is not fully understood either. Current evidence suggests that two proteins, the voltage-dependent anion channel (VDAC), located in the outer mitochondrial membrane, and the adenine nucleotide translocase (ANT-1), located in the inner mitochondrial membrane, combine to form a pore that spans both membranes. [Pg.107]

The answer is b. (Murray, pp 505-626. Scriver, pp 4029-4240. Sack, pp 121-138. Wilson, pp 287-320.) A deficiency in carnitine, carnitine acyl-transferase 1, carnitine acyltransferase 11, or acylcarnitine translocase can lead to an inability to oxidize long-chain fatty acids. This occurs because all of these components are needed to translocate activated long-chain (>10 carbons long) fatty acyl CoA across mitochondrial inner membrane into the matrix where P oxidation takes place. Once long-chain fatty acids are coupled to the sulfur atom of CoA on the outer mitochondrial membrane, they can be transferred to carnitine by the enzyme carnitine acyltransferase I, which is located on the cytosolic side of the inner mitochondrial membrane. Acyl carnitine is transferred across the inner membrane to the matrix surface by translocase. At this point the acyl group is reattached to a CoA sulfhydryl by the carnitine acyltransferase 11 located on the matrix face of the inner mitochondrial membrane. [Pg.295]

Mitochondria and cell death Although oxidative phosphorylation is a mitochondrial process, most ATP utilization occurs outside of the mitochondrion. ATP synthesized from oxidative phosphorylation is actively transported from the matrix to the intermembrane space by adenine nucleotide translocase (ANT). Porins form voltage-dependent anion channels (VDAC) through the outer mitochondrial membrane for the diffusion of H2O, ATP metabolites, and other ions. Under certain types of stress, ANT, VDAC, and other proteins form a nonspecific open channel known as the mitochondrial permeability transition pore. This pore is associated with events that lead rapidly to necrotic cell death. [Pg.381]

Carnitine palmitoyltransferase I (CPTI also called carnitine acyltransferase I, CATI), the enzyme that transfers long-chain fatty acyl groups from CoA to carnitine, is located on the outer mitochondrial membrane (Fig. 23.5). Fatty acylcamitine crosses the inner mitochondrial membrane with the aid of a translocase. The fatty acyl group is transferred back to CoA by a second enzyme, carnitine palmitoyl-transferase II (CPTII or CATII). The carnitine released in this reaction returns to the cytosolic side of the mitochondrial membrane by the same translocase that brings fatty acylcamitine to the matrix side. Long-chain fatty acyl CoA, now located within the mitochondrial matrix, is a substrate for (3-oxidation. [Pg.423]

Figure 3. Schematic architecture of mitochondrial protein complexes. A transmembrane channel, called the permeability transition pore (FTP), is formed at the contaa sites between the inner and outer mitochondrial membrane (OM) of the mitochondria. The core components of PTP are the voltage-dependent anion channel (VDAC) in the outer membrane and the adenine nucleotide translocator (ANT) in the inner membrane (IM). VDAC allows diilusion of small molecules (<5 kDa), however ANT is only permeable to a few selected ions and metabolites and is responsible for maintaining the proton concentration gradient (pH) and the membrane elearic potential (A P,J. PTP is sometimes connected to destruction of permeability barrier and loss of the inner membrane potential and eventually results in mitochondrial membrane permeability transition during apoptosis and other specialized forms of cell death. Bax, Bak, Bc1-Xl and Bcl-2 locate in the outer membrane and may regulate the outer membrane permeability. The translocase of the outer membrane (TOM) and the translocase of the inner membrane (TlM) mediate protein import pathway in the mitochondria. Cy-D, cyclophilin D PBR, peripheral benzodiazepine receptor HK, hexokinase mtHSP70, mitochondrial heat shock protein 70. Figure 3. Schematic architecture of mitochondrial protein complexes. A transmembrane channel, called the permeability transition pore (FTP), is formed at the contaa sites between the inner and outer mitochondrial membrane (OM) of the mitochondria. The core components of PTP are the voltage-dependent anion channel (VDAC) in the outer membrane and the adenine nucleotide translocator (ANT) in the inner membrane (IM). VDAC allows diilusion of small molecules (<5 kDa), however ANT is only permeable to a few selected ions and metabolites and is responsible for maintaining the proton concentration gradient (pH) and the membrane elearic potential (A P,J. PTP is sometimes connected to destruction of permeability barrier and loss of the inner membrane potential and eventually results in mitochondrial membrane permeability transition during apoptosis and other specialized forms of cell death. Bax, Bak, Bc1-Xl and Bcl-2 locate in the outer membrane and may regulate the outer membrane permeability. The translocase of the outer membrane (TOM) and the translocase of the inner membrane (TlM) mediate protein import pathway in the mitochondria. Cy-D, cyclophilin D PBR, peripheral benzodiazepine receptor HK, hexokinase mtHSP70, mitochondrial heat shock protein 70.
Fig. 3. Fatty acid degradation. Role of carnitine in the transport of long-chain fatty acids through the inner mitochondrial membrane. Carnitine-acylcarnitine translocase is an integral membrane exchange transport system. Carnitine acyltransferases I and II are located on the outer and inner surfaces, respectively, of the inner mitochondrial membrane. Fig. 3. Fatty acid degradation. Role of carnitine in the transport of long-chain fatty acids through the inner mitochondrial membrane. Carnitine-acylcarnitine translocase is an integral membrane exchange transport system. Carnitine acyltransferases I and II are located on the outer and inner surfaces, respectively, of the inner mitochondrial membrane.
Carnitine serves as a cofactor for several enzymes, including carnitine translo-case and acyl carnitine transferases I and II, which are essential for the movement of activated long-chain fatty acids from the cytoplasm into the mitochondria (Figure 11.2). The translocation of fatty acids (FAs) is critical for the genaation of adenosine triphosphate (ATP) within skeletal muscle, via 3-oxidation. These activated FAs become esterified to acylcamitines with carnitine via camitine-acyl-transferase I (CAT I) in the outer mitochondrial membrane. Acylcamitines can easily permeate the membrane of the mitochondria and are translocated across the membrane by carnitine translocase. Carnitine s actions are not yet complete because the mitochondrion has two membranes to cross thus, through the action of CAT II, the acylcar-nitines are converted back to acyl-CoA and carnitine. Acyl-CoA can be used to generate ATP via 3-oxidation, Krebs cycle, and the electron transport chain. Carnitine is recycled to the cytoplasm for fumre use. [Pg.202]

Figure 7.11 Mechanism of transport of long-chain fatty adds across the inner mitochondrial membrane as fatty acyl carnitine. CRT is the abbreviation for carnitine palmitoyl transferase. CPT-I resides on the outer surface of the inner membrane, whereas CPT-II resides on the inner side of the inner membrane of the mitochondria. Transport across the inner membrane is achieved by a carrier protein known as a translocase. FACN - fatty acyl carnitine, CN - carnitine. Despite the name, CRT reacts with long-chain fatty acids other than palmitate. CN is transported out of the mitochondria by the same translocase. Figure 7.11 Mechanism of transport of long-chain fatty adds across the inner mitochondrial membrane as fatty acyl carnitine. CRT is the abbreviation for carnitine palmitoyl transferase. CPT-I resides on the outer surface of the inner membrane, whereas CPT-II resides on the inner side of the inner membrane of the mitochondria. Transport across the inner membrane is achieved by a carrier protein known as a translocase. FACN - fatty acyl carnitine, CN - carnitine. Despite the name, CRT reacts with long-chain fatty acids other than palmitate. CN is transported out of the mitochondria by the same translocase.
Figure 17.3. Permeability transition pore (PTP). The PTP consists of voltage-dependent anion channel (VDAC), adenine nucleotide translocase (ANT) and several associated molecules including cyclophilin D (CypD) and peripheral benzodiazepine receptor (PBR). IMM, inner mitochondrial membrane OMM, outer mitochondrial membrane CytC, cytochrome c. Figure 17.3. Permeability transition pore (PTP). The PTP consists of voltage-dependent anion channel (VDAC), adenine nucleotide translocase (ANT) and several associated molecules including cyclophilin D (CypD) and peripheral benzodiazepine receptor (PBR). IMM, inner mitochondrial membrane OMM, outer mitochondrial membrane CytC, cytochrome c.
Fig. 21.13. Transport of compounds across the inner and outer mitochondrial membranes. The electrochemical potential gradient drives the transport of ions across the inner mitochondrial membrane on specific translocases. Each translocase is composed of specific membrane-spanning helices that bind only specific compounds (ANT adenine nucleotide translocase). In contrast, the outer membrane contains relatively large unspecific pores called VDAC (voltage-dependent anion channels) through which a wide range of ions diffuse. These bind cytosolic proteins such as hexokinase (HK), which enables HK to have access to newly exported ATP. Fig. 21.13. Transport of compounds across the inner and outer mitochondrial membranes. The electrochemical potential gradient drives the transport of ions across the inner mitochondrial membrane on specific translocases. Each translocase is composed of specific membrane-spanning helices that bind only specific compounds (ANT adenine nucleotide translocase). In contrast, the outer membrane contains relatively large unspecific pores called VDAC (voltage-dependent anion channels) through which a wide range of ions diffuse. These bind cytosolic proteins such as hexokinase (HK), which enables HK to have access to newly exported ATP.

See other pages where Translocase of the outer mitochondrial membrane is mentioned: [Pg.72]    [Pg.210]    [Pg.1019]    [Pg.106]    [Pg.85]    [Pg.72]    [Pg.210]    [Pg.1019]    [Pg.106]    [Pg.85]    [Pg.69]    [Pg.885]    [Pg.135]    [Pg.499]    [Pg.312]    [Pg.359]    [Pg.25]    [Pg.117]    [Pg.316]    [Pg.337]    [Pg.4]    [Pg.7]    [Pg.144]    [Pg.67]    [Pg.2]    [Pg.5]    [Pg.262]    [Pg.290]    [Pg.2231]    [Pg.12]    [Pg.151]    [Pg.226]    [Pg.264]   
See also in sourсe #XX -- [ Pg.1018 , Pg.1019 ]

See also in sourсe #XX -- [ Pg.1018 , Pg.1019 ]

See also in sourсe #XX -- [ Pg.1018 , Pg.1019 ]




SEARCH



Membranes Mitochondrial membrane

Mitochondrial membranes

Outer mitochondrial membrane

The Outer Membrane

Translocase of the outer mitochondrial

Translocase-of-the-outer membrane

Translocases

© 2024 chempedia.info