The intracellular distribution of polyribosomes synthesizing mitochondrial proteins

Gaitskhoki, V. S.; Kisselev, O.I.; Klimov, N. A.; Monakhov, N. K.; Mukha, G.V.; Neifakh, S. A.

doi:10.1016/0014-5793(74)80989-0

Cited by 13 publications

(4 citation statements)

References 6 publications

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“…Evidence for the existence of such ribosomes in yeast cells has been presented [17] and the suggestion was further made that completed translation products may be transferred directly to the mitochondria without becoming free in the cytoplasm. A similar suggestion was been made with respect to synthesis of mitochondrial proteins in rat liver [18]. There is, however, considerable conflicting evidence.…”

Section: Discussionmentioning

confidence: 70%

Studies of the Selective Permeation of Radioactively Labelled Aspartate Aminotransferase Isozymes into Mitochondria in vitro

Marra¹,

Doonan²,

Saccone³

et al. 1978

Eur J Biochem

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1. Radioactively labelled cytoplasmic and mitochondrial aspartate aminotransferases from rat liver were prepared by reduction of the cofactor-apoprotein linkages with sodium borotritiide.2. Both the native and the radioactively labelled forms of the mitochondrial isozyme associated with intact mitochondria, the degree of association decreasing with increasing buffer concentration in the suspension medium. The cytoplasmic isozyme did not associate with mitochondria under the same conditions.3. It was shown, using the native mitochondrial isozyme, that at low buffer concentration the association was mainly due to external binding of the isozyme to the organelles. At higher buffer concentration association was due entirely to entry of the isozyme into the mitochondria. It was concluded that association of radioactivity with the mitochondrial pellet after incubation of the mitochondria with labelled mitochondrial isozyme in 20 mM Tris/HCl buffer pH 7.4 provided a measure of entry of the isozyme into the organelles.4. The amount of labelled isozyme entering the mitochondria showed a hyperbolic dependence on amount of externally added aspartate aminotransferase and reached a limit of approximately 1 pg of enzyme/mg mitochondrial protein.5. The entry process was rapid, being essentially complete in the time required to mix the enzyme with the mitochondrial suspension and then to sediment the mitochondria. 6. At a constant level of externally added isozyme, the amount entering the mitochondria varied with temperature in a biphasic manner.7. The extent of uptake of the mitochondrial isozyme was not affected by the presence of the uncoupler carbonyl cyanide p-trifluoromethoxyphenylhydrazone.8. The relevance of these results to the mechanism of incorporation of cytoplasmically synthesised proteins into mitochondria in vivo is discussed.

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Section: Discussionmentioning

confidence: 70%

Studies of the Selective Permeation of Radioactively Labelled Aspartate Aminotransferase Isozymes into Mitochondria in vitro

Marra¹,

Doonan²,

Saccone³

et al. 1978

Eur J Biochem

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“…From the results given here, no hypothesis can be formulated about the mechanism of the penetration of the mitochondrial membranes by aspartate aminotransferase; this must await further studies. It should, however, be pointed out that the mitochondrial pre-1977 paration used could have been contaminated with cytoplasmic ribosomes (Gaitskhoki et al, 1974;Kellems et al, 1975) and hence it is possible that these contribute to the overall process. The probable involvement of ribosomes in transfer of proteins to mitochondria is already apparent from the work of Kadenbach (1967) and of Godinot & Lardy (1973).…”

Section: Discussionmentioning

confidence: 99%

Selective permeability of rat liver mitochondria to purified aspartate aminotransferases in vitro

Marra¹,

Doonan²,

Saccone³

et al. 1977

Biochemical Journal

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1. A method was devised to allow determination of intramitochondrial aspartate amino-transferase activity in suspensions of intact mitochondria. 2. Addition of purified rat liver mitochondrial aspartate aminotransferase to suspensions of rat liver mitochondria caused an apparent increase in the intramitochondrial enzyme activity. No increase was observed when the mitochondria were preincubated with the purified cytoplasmic isoenzyme. 3. These results suggest that mitochondrial aspartate aminotransferase, but not the cytoplasmic isoenzyme, is able to pass from solution into the matrix of intact rat liver mitochondria in vitro. 4. This system may provide a model for studies of the little-understood processes by which cytoplasmically synthesized components are incorporated into mitochondria in vivo.

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“…It is seen that mt polysomes sediment in a sucrose gradient rather slowly. Their sedimentation coefficients are in the range of 80-1908 corresponding to 2-9 monoribosomes per one mRNA molecule (17). On dissociation mt polysomes release 28S and 40S subparticles which were demonstrated with the aid of analytical ultracentrifugation (fig.…”

Section: ]Resultsmentioning

confidence: 96%

Isolation and partial characterization of poly (A)-containing 7.5S messenger RNA from rat liver mitochondria

1977

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Poly(A)-containing low molecular weight (7.5S) messenger RNA was isolated in a highly purified form from both polyribosomes and post-polysomal supernatant of rat liver mitochondria. Both mRNA's contain rather short poly(A) tracts (40-70 mononucleotides) according to a profile of their elution from poly(U)-Sepharose column with a gradient of formamide concentration. Both mRNA's when added to a preincubated mitochondrial lysate programmed the synthesis of a hydrophobic polypeptide of a molecular weight about 9000 daltons which was soluble in the neutral chloroform-methanol mixture.

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The intracellular distribution of polyribosomes synthesizing mitochondrial proteins

Cited by 13 publications

References 6 publications

Studies of the Selective Permeation of Radioactively Labelled Aspartate Aminotransferase Isozymes into Mitochondria in vitro

Studies of the Selective Permeation of Radioactively Labelled Aspartate Aminotransferase Isozymes into Mitochondria in vitro

Selective permeability of rat liver mitochondria to purified aspartate aminotransferases in vitro

Isolation and partial characterization of poly (A)-containing 7.5S messenger RNA from rat liver mitochondria

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