Coupling Factor for Photophosphorylation in Bean Etioplasts and Chloroplasts

Horak, Arnost; Hill, Robert D.

doi:10.1139/o71-030

Cited by 15 publications

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“…Bean (Phaseolus vulgaris L.) etioplasts and chloroplasts were prepared, and the coupling factor was extracted with EDTA as previously described (12).…”

Section: Methodsmentioning

confidence: 99%

“…ATPase activity of the DTT-activated EDTA extracts was measured according to McCarty and Racker (24) under conditions described in the previous paper (12). RuDP carboxylase of the extracts was assayed according to Bradbeer (2).…”

Section: Methodsmentioning

confidence: 99%

“…Evidence suggests that this factor may be responsible for phosphorylation of ADP (23,28). In a previous paper (12) we have shown that extracts from bean etioplasts and chloroplasts contain a similar factor that stimulated photophosphorylation in partially deficient chloroplast residues. Both extracts contained a Ca'+-dependent, DIT2-activated ATPase with properties similar to the spinach chloroplast ATPase (24).…”

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confidence: 88%

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Adenosine Triphosphatase of Bean Plastids

Horak

Hill

1972

Plant Physiol.

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Extracts of bean (Phaseolus vulgaris L.) etioplasts and chloroplasts contain a dithiothreitol-activated Ca2+-dependent adenosine triphosphatase which is inhibited by . The chloroplast and etioplast enzymes have identical RF values upon disc gel electrophoresis. Optimum extraction of the enzyme from either plastid preparation is accomplished with 1 mM ethylenediamine tetraacetic acid. Photophosphorylation capacity can be partially restored to depleted chloroplast preparations by addition of either the chloroplast or etioplast extract. These results suggest that the adenosine triphosphatase from etioplasts and chloroplasts represents a modified coupling factor for photophosphorylation.The specific activity of the adenosine triphosphatase in the extracts of plastids increases upon greening of etiolated plants due to protein synthesis. This light-induced increase is inhibited by both chloramphenicol and cycloheximide, specific inhibitors of chloroplastic and cytoplasmic protein synthesis. There is no accumulation of adenosine triphosphatase in postribosomal supernatants of cycloheximide or chloramphenicol treated leaves. The results indicate that both the chloroplastic and the cytoplasmic ribosomal systems are required for the formation of the chloroplast adenosine triphosphatase.In the development of photosynthetic activity during the greening of bean leaves, photophosphorylation capacity increases in proportion to the increase of chlorophyll in the tissue (9). In terms of the plastid's ability to phosphorylate ADP, this could be interpreted in one of two ways. The etioplast may contain the enzymes or components necessary for phosphorylation but lack chlorophyll and possibly other electron transport carriers. Alternatively, the etioplasts may be deficient in components necessary for phosphorylation in addition to their lack of chlorophyll.A factor isolated from spinach chloroplasts that has latent ATPase activity has been shown to stimulate photophosphorylation in partially deficient chloroplast residues (28). Evidence suggests that this factor may be responsible for phosphorylation of ADP (23,28). In a previous paper (12) we have shown that extracts from bean etioplasts and chloroplasts contain a similar factor that stimulated photophosphorylation in I

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“…Bean (Phaseolus vulgaris L.) etioplasts and chloroplasts were prepared, and the coupling factor was extracted with EDTA as previously described (12).…”

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 88%

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Adenosine Triphosphatase of Bean Plastids

Horak

Hill

1972

Plant Physiol.

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confidence: 97%

“…This demonstrated that the unit of membrane assembly in maize thylakoids is different from the unit of photosynthetic function of these membranes. The coupling factor for phosphorylation also occurs in bean etioplasts (6).A/B phos3 is the production by chloroplast thylakoids of ATP upon transfer of membrane vesicles from an acidic to an alkaline solution in the presence of ADP and inorganic phosphate (7). This reaction occurs in darkness and is entirely independent of the capture of quanta by Chl.…”

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confidence: 99%

Steps in the Acquisition of Photosynthetic Competence by Plastids of Maize

Forger

Bogorad²

1973

Plant Physiol.

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Coupling factor particles are associated with membranes of maize etioplasts (Lockshin et al., 1971. Biochim. Biophys. Acta 226: 366-382). In addition, several, but not all, of the polypeptides found in the photosynthetic lamellae of maize chloroplasts are present in etioplasts.During the photoregulated maturation of chloroplasts from etioplasts, the membranes of the organelie acquire the capacity to carry on acid to base phosphorylation. (9) have shown that the coupling factor required for photophosphorylation is associated with the membranes of the etioplasts of dark-grown maize. This demonstrated that the unit of membrane assembly in maize thylakoids is different from the unit of photosynthetic function of these membranes. The coupling factor for phosphorylation also occurs in bean etioplasts (6).A/B phos3 is the production by chloroplast thylakoids of ATP upon transfer of membrane vesicles from an acidic to an alkaline solution in the presence of ADP and inorganic phosphate (7). This reaction occurs in darkness and is entirely independent of the capture of quanta by Chl. Etioplast membranes are incapable of carrying out A/B phos even though they contain the coupling factor which is required for this process (5). However, the volume of these membranes fails to change regardless of the osmotic environment, unlike thylakoids of green plastids. Plastid fragments obtained from maize seedlings grown in the dark for 7 days and then illuminated for a few hours can carry on A/B phos. It has been shown (5) MATERIALS AND METHODSPlant material, growth and greening conditions, plastid isolation, and assay of A/B phos activity were the same as described previously (5).PPV determinations were made as previously described (5), except that in some instances thrombocytocrits were employed instead of Stafford-Shevsky and McNaught tubes. The former allow volume determinations with an accuracy of ±3% under the condition of the experiments.For protein and lipid determinations, plastid thylakoid preparations were purified by means of sucrose density gradients. The plastids were isolated as described earlier (5), ruptured osmotically in 10 mm NaCl and homogenized. The resulting suspension was layered onto continuous gradients which ranged from 25 to 68% (w/v) of sucrose in 0.05 M HEPES, pH 7.7, and 1 mm MgCl2. The gradients were centrifuged in a Beckman SW 27 rotor at 25,000 rpm for 90 min. The purified pigmented fragments were removed with a syringe, diluted with 10 mm NaCl, and sedimented by centrifugation in a Sorvall SS-34 rotor at 12,000g for 5 min. After resuspension of the resulting pellet in 10 mm NaCl, the fragments were ready for use. All steps were carried out at or near 0 C.The isolated and purified fragments to be used for fatty acid determinations were saponified under N2 with 50% methanolic KOH (50% methanol containing 5% KOH) for 2 hr at 100 C. The nonsaponifiable fraction was exhaustively extracted into petroleum ether and discarded. The KOH-methanol solution containing saponifiable lipids was acidified w...

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Development of Chloroplast Structure and Function

Boardman¹

1977

Photosynthesis I

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Coupling Factor for Photophosphorylation in Bean Etioplasts and Chloroplasts

Cited by 15 publications

References 0 publications

Adenosine Triphosphatase of Bean Plastids

Adenosine Triphosphatase of Bean Plastids

Steps in the Acquisition of Photosynthetic Competence by Plastids of Maize

Development of Chloroplast Structure and Function

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