Lysophospholipase activity in cell-wall fragments contaminating mitochondrial fractions of Neurospora crassa

Degoede, Gw; Samallo, John; Holtrop, Marijke; Scherphof, Gl

doi:10.1016/0005-2760(76)90188-0

Cited by 6 publications

(1 citation statement)

References 20 publications

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“…After protein synthesis was terminated by addition of cycloheximide, the postribosomal supcrnatant was prepared and combined with isolated mitochondria. These had becn purified by sucrose-density-gradient centrifugation to remove contaminating cell-wall fragments and lysophospholipase activity [45]. This reconstituted system was then incubated to allow apocytochrome c present in the extramitochondrial fraction to be taken up by mitochondria and to be converted to holocytochrome c. The reaction was stopped after various time periods by chilling the samples ; mitochondria and supernatant were separated again.…”

Section: Kinetics Of Import Of Cytochrome C Into Mitochondria In Vitromentioning

confidence: 99%

Assembly of Cytochrome c. Apocytochrome c Is Bound to Specific Sites on Mitochondria before Its Conversion to Holocytochrome c

Hennig

Neupert

1981

European Journal of Biochemistry

157

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Transport of apocytochrome c across the outer mitochondrial membrane and conversion to holocytochrome c were studied in vitro. Apocytochrome c was synthesized in a cell‐free homogenate from Neurospora crassa. Transfer in vitro was accomplished in a reconstituted system consisting of the postribosomal supernatant of the cell‐free homogenate and of isolated and purified mitochondria from Neurospora. The reconstituted system has the following characteristics: Apocytochrome c is rapidly cleared from the supernatant and holocytochrome c appears in the mitochondria with the same kinetics. More than 80% of the apocytochrome c employed is converted to holocytochrome c. No transient accumulation of apocytochrome c is found in mitochondria. The heme group becomes covalently linked to apocytochrome c in the reconstituted system as demonstrated by analysis of tryptic peptide maps of the apoprotein and holoprotein. Deuterohemin added to the reconstituted system but not deuteroporphyrin inhibits the formation of holocytochrome c. This inhibition is reversed by protohemin. In the presence of deuterohemin about half of the apocytochrome c remains in the supernatant; the other half becomes associated with the mitochondria. The latter portion is tightly bound and is specifically released upon incubation of the mitochondria with excess apocytochrome c. It is converted to holocytochrome c after addition of protohemin. We conclude from these observations that apocytochrome c is transported across the outer mitochondrial membrane via receptor sites. In the presence of the heme analogue deuterohemin, binding to the receptor sites on the cytoplasmic surface of the outer mitochondrial membrane still takes place but translocation does not. The latter step is apparently coupled to the covalent linkage of the heme group. We suggest that the formation of the thioether bonds between apoprotein and heme is catalysed by an enzyme in the intermembrane space and that deuterohemin can compete with protohemin for binding to the enzyme. Finally, the data indicate that it is the heme group and not the porphyrin group which is coupled to the apoprotein.

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Section: Kinetics Of Import Of Cytochrome C Into Mitochondria In Vitromentioning

confidence: 99%

Assembly of Cytochrome c. Apocytochrome c Is Bound to Specific Sites on Mitochondria before Its Conversion to Holocytochrome c

Hennig

Neupert

1981

European Journal of Biochemistry

157

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Studies on phospholipase activities inneurospora crassa mycelia

Chakravarti

Chakrabarti

1980

Lipids

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Phospholipase A activity has been detected in mycelial homogenate of Neurospora crassa. A submycelial fraction, obtained by differential centrifugation containing the highest specific activity of phospholipase A has been shown to contain ca. 66% phospholipase A and 34% phospholipase A activity along with lysophospholipase and degergent-stimulated phospholipase D activity. Phospholipase A activity bound to N. crassa mycelia also has been observed.

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The involvement of the lipid phase transition in the plasma-induced dissolution of multilamellar phosphatidylcholine vesicles

Scherphof¹,

Morselt²,

Regts³

et al. 1979

Biochimica et Biophysica Acta (BBA) - Biomembranes

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Lysophospholipase activity in cell-wall fragments contaminating mitochondrial fractions of Neurospora crassa

Cited by 6 publications

References 20 publications

Assembly of Cytochrome c. Apocytochrome c Is Bound to Specific Sites on Mitochondria before Its Conversion to Holocytochrome c

Assembly of Cytochrome c. Apocytochrome c Is Bound to Specific Sites on Mitochondria before Its Conversion to Holocytochrome c

Studies on phospholipase activities inneurospora crassa mycelia

The involvement of the lipid phase transition in the plasma-induced dissolution of multilamellar phosphatidylcholine vesicles

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