Studies on the biosynthesis of mitochondrial malate dehydrogenase and the location of its synthesis in the liver cell of the rat

Bingham, R. W.; Campbell, P. N.

doi:10.1042/bj1260211

Cited by 21 publications

(9 citation statements)

References 23 publications

(17 reference statements)

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“…Immunological studies on the synthesis of mitochondrial glutamate dehydrogenase [13] and of mitochondrial and cytoplasmic isoenzymes of malate dehydrogenase [25,26] in liver led to the proposal that the synthesis of these enzymes took place on membrane-bound ribosomes. It ~7as further suggested that the microsomal vesicles contained these proteins in an enzymatically active form.…”

Section: Incubation Of a Cell-free Homogenate With [3h]-mentioning

confidence: 99%

Transport of Cytoplasmically Synthesized Proteins into the Mitochondria in a Cell Free System from Neurospora crassa

Harmey

Hallermayer

Korb

et al. 1977

European Journal of Biochemistry

110

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Synthesis and transport of mitochondrial proteins were followed in a cell-free homogenate of Neurospora crussa in which mitochondrial translation was inhibited. Proteins synthesized on cytoplasmic ribosomes are transferred into the mitochondrial fraction. The relative amounts of proteins which are transferred in vitro are comparable to those transferred in whole cells.Cycloheximide and puromycin inhibit the synthesis of mitochondrial proteins but not their transfer into mitochondria.The transfer of immunoprecipitablc mitochondrial proteins was demonstrated for matrix proteins, carboxyatractyloside-binding protein and cytochrome c.Import of proteins into mitochondria exhibits a degree of specificity. The transport mechanism differentiales between newly synthesized proteins and preexistent mitochondrial proteins, at least in the case of matrix proteins.In the cell-free homogenate membrane-bound ribosonies are more active in the synthesis of mitochondrial proteins than are free ribosomes. The finished translation products appear to be released from the membrane-bound ribosomes into the cytosol rather than into the membrane vesicles.The results suggest that the transport of cytoplasniically synthesized mitochondrial proteins is essentially independent of cytoplasmic translation ; that cytoplasmically synthesized mitochondrial proteins exist in an extramitochondrial pool prior to import; that the site of this pool is the cytosol for at least some of the mitochondrial proteins; and that the precursors in the extramitochondrial pool differ in structure or conformation from the functional proteins in the mitochondria.In the preceding paper we studied the transport of cytoplasmically synthesized proteins into the mitochondria in intact cells of Neurosporu crassu [l]. la whole cells, the processes of synthesis and transport are not easily separated. Furthermore, post-labelling fractionation artifacts may obscure the intracellular location of mitochondrial proteins which are on their path from the site of synthesis to the site of function.In considering systems in vitro a number of possibilities exist, ranging Crom cell-free homogenates to reconstituted systems involving isolated and purified protein and organelle components. In the present study we have investigated synthesis and transport in a cell-free homogenate. We. have employed this system in an attempt lo decide between two mechanisms currently proposed for the transport of mitochondria] proteins. The first mechanism is based on observations with whole IC'emrospora cells [l]. This mechanism proposes the existence of extramitochondrial pools of mitochondrial proteins from which they are imported into the mitochondria. The second mechanism is that proposed by Butow and his colleagues [3 -61. This latter mechanism proposes a special class of cytoplasmic ribosomes which are attached to the mitochondria at specific sites. The nascent polypeptides from these ribosomes are discharged in a vectorial manner into the mitochondria.The results we present here support our earli...

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Section: Incubation Of a Cell-free Homogenate With [3h]-mentioning

confidence: 99%

Transport of Cytoplasmically Synthesized Proteins into the Mitochondria in a Cell Free System from Neurospora crassa

Harmey

Hallermayer

Korb

et al. 1977

European Journal of Biochemistry

110

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“…newly synthesized proteins [4], and from the 100 000 g supernatant of the liver homogenate (which contained both extra-and intramitochondrial isozymes). As calculated from enzyme activity determinations before and after immunoprecipitation with the two antisera, the microsomal fraction contains s-MDH as well as m-MDH.…”

Section: Resultsmentioning

confidence: 99%

“…Bingham et at. [4] have already reported synthesis of the mitochondrial MDH in vitro by isolated microsomes. The present data indicate that this newly synthesized enzyme may be considered as the precursor of mitochondrial malate dehydrogenase.…”

Section: Resultsmentioning

confidence: 99%

“…Isolated rat liver mitochondria incorporate negligible amounts of 14C-labelled amino acids into the soluble proteins as, e.g., cytochrome c and malate dehydrogenase [1]. Gonzfiles-Cadavid et al [2] and Kadenbach et al [3] showed by in vivo pulse-labelling experiments that microsomal cytochrome c becomes labelled earlier and to a higher extent than mitochondrial cytochrome c. Recently Bingham et al [4] were able to demonstrate that mitochondrial malate dehydrogenase is one of the proteins synthesized in vitro by the microsomal fraction from rat liver.…”

Section: Introduction 2 Methodsmentioning

confidence: 99%

“…At ~ different time intervals the animals were killed and the microsomal fraction from 40 g of liver was prepared according to Bingham et al [4]. The isolated microsomes were then extracted with 1% Triton X-100 in 0.15 M NaC1 [4].…”

Section: Introduction 2 Methodsmentioning

confidence: 99%

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Studies on the biosynthesis of malate dehydrogenase isozymes in rabbit liver

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Reconstitution and Physiological Protein Translocation Processes

Etemadi

1989

Subcellular Biochemistry

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FIGURE 1. Some models for membrane-protein interaction during translocation of secretory and! or transmembrane integral proteins are reproduced. In all schemes, unless otherwise stated, the lower side and the upper side represent the cytoplasmic (cis) and the extracytoplasmic (trans) compartment, respectively. In the loop model A (DiRienzo et al. 1978;Inouye and Halegoua 1980), positively charged amino acid(s) at the N terminus of the signal sequence react with negatively charged head groups of membrane phospholipids. The hydrophobic part of the signal sequence would interact with and loop back in the hydrophobic core of the membrane, bending being due to the presence of a glycine or proline residue in the hydrophobic segment of the signal. Chain elongation would continue until the cleavage site reaches the side remote from the cytoplasm where processing occurs. In model B (Garnier et at., 1980) the signal sequence as a double amphipathic structure inserts in the membrane. Its hydrophobic core has an a-helical or extended conformation and its N terminus is extracytoplasmic. Only after this insertion ribophorin (R) assembly around the signal peptide occurs and interaction of ribophorins, with the ribosomes, leads to the formation of a channel through which the protein is translocated. In the helical hairpin model, C (Engelman and Steitz, 1981), the signal sequence and the N-terminal segment of the mature part of a nascent secretory or transmembrane integral protein form a hydrophobic (H) and a polar (P) helix, respectively, which together exhibit a helical hairpin conformation. The "helical hairpin" is inserted into the membrane in such a way that the N terminus of the signal sequence is cytoplasmic, as in the loop model. Continuation of translation extrudes residues of the polar helix in the trans side, while

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Studies on the biosynthesis of mitochondrial malate dehydrogenase and the location of its synthesis in the liver cell of the rat

Cited by 21 publications

References 23 publications

Transport of Cytoplasmically Synthesized Proteins into the Mitochondria in a Cell Free System from Neurospora crassa

Transport of Cytoplasmically Synthesized Proteins into the Mitochondria in a Cell Free System from Neurospora crassa

Studies on the biosynthesis of malate dehydrogenase isozymes in rabbit liver

Reconstitution and Physiological Protein Translocation Processes

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