scholarly journals Identification of the putative hexose-phosphate translocator of amyloplasts from cauliflower buds

1993 ◽  
Vol 294 (1) ◽  
pp. 15-17 ◽  
Author(s):  
O Batz ◽  
R Scheibe ◽  
H E Neuhaus
Keyword(s):  
Membrane Protein ◽  
Starch Synthesis ◽  
Dihydroxyacetone Phosphate ◽  
Radioactive Label ◽  
Hexose Phosphate ◽  
Phosphate Translocator

Starch synthesis in amyloplasts isolated from cauliflower buds is strongly inhibited by the addition of micromolar concentrations of 4,4′-di-isothiocyano-2,2′-stilbenedisulphonic acid (DIDS). Using [3H]DIDS it was possible to label specifically a 31.6 kDa membrane protein of the envelope fraction of isolated amyloplasts. The intensity of the radioactive label was decreased in the presence of glucose 6-phosphate or dihydroxyacetone phosphate, indicating that this protein might be the amyloplastic hexosephosphate translocator.

scholarly journals Analysis of carbohydrate transport across the envelope of isolated cauliflower-bud amyloplasts

1995 ◽  
Vol 307 (2) ◽  
pp. 521-526 ◽  
Author(s):  
T Möhlmann ◽  
O Batz ◽  
U Maass ◽  
H E Neuhaus
Keyword(s):  
Envelope Protein ◽  
Starch Synthesis ◽  
Specific Inhibitor ◽  
Competitive Inhibitor ◽  
Transport Proteins ◽  
Dihydroxyacetone Phosphate ◽  
Envelope Membrane ◽  
Phosphate Translocator ◽  
Low Concentrations ◽  
Carbohydrate Transport

Using isolated amyloplasts from cauliflower buds, we have characterized the interaction and transport of various carbohydrates across the envelope membrane of a heterotrophic plastid. According to our results, glucose 6-phosphate (Glc6P) and glucose 1-phosphate (Glc1P) do not share the same transport protein for uptake into cauliflower-bud amyloplasts. Glc6P-dependent starch synthesis is strongly inhibited in the presence of dihydroxyacetone phosphate (DHAP) or 4,4′-di-isothiocyano-2,2′- stilbenedisulphonic acid (DIDS), whereas Glc1P-dependent starch synthesis is hardly affected by these compounds. Analysis of the Glc6P uptake into proteoliposomes reconstituted from the envelope proteins of cauliflower-bud amyloplasts indicate that Glc6P is taken up in a counter-exchange mode with Pi, DHAP or Glc6P, whereas Glc1P does not act as a counter-exchange substrate. Pi is a strong competitive inhibitor of Glc6P uptake (Ki 0.8 mM) into proteoliposomes, whereas Glc1P does not significantly inhibit Glc6P transport. Beside a hexose-phosphate translocator, these amyloplasts possess an envelope protein mediating the transport of glucose across the membrane. This translocator exhibits an apparent Km for glucose of 2.2 mM and is inhibited by low concentrations of phloretin, known to be a specific inhibitor of glucose-transport proteins. Maltose inhibits the uptake of glucose (Ki 2.3 mM), indicating that both carbohydrates share the same translocator.

scholarly journals Induction of Hexose-Phosphate Translocator Activity in Spinach Chloroplasts

1995 ◽  
Vol 109 (1) ◽  
pp. 113-121 ◽  
Author(s):  
W. P. Quick ◽  
R. Scheibe ◽  
H. E. Neuhaus
Keyword(s):  
Spinach Chloroplasts ◽  
Hexose Phosphate ◽  
Phosphate Translocator

scholarly journals Reconstitution of the hexose phosphate translocator from the envelope membranes of wheat endosperm amyloplasts

1996 ◽  
Vol 319 (3) ◽  
pp. 717-723 ◽  
Author(s):  
Ian J TETLOW ◽  
Caroline G BOWSHER ◽  
Michael J EMES
Keyword(s):  
Inorganic Phosphate ◽  
Competitive Inhibitor ◽  
Dihydroxyacetone Phosphate ◽  
Carrier Protein ◽  
Sugar Phosphate ◽  
Wheat Endosperm ◽  
Single Carrier ◽  
Phosphate Translocator ◽  
Envelope Membranes ◽  
Hexose Phosphates

Amyloplasts were isolated and purified from wheat endosperm and the envelope membranes reconstituted into liposomes. Envelope membranes were solubilized in n-octyl β-D-glucopyranoside and mixed with liposomes supplemented with 5.6 mol% cholesterol to produce proteoliposomes of defined size, which showed negligible leakage of internal substrates. Transport experiments with proteoliposomes revealed a counter-exchange of glucose 1-phosphate (Glc1P), glucose 6-phosphate (Glc6P), inorganic phosphate (Pi), 3-phosphoglycerate and dihydroxyacetone phosphate. The Glc1P/Pi counter-exchange reaction exhibited an apparent Km for Glc1P of 0.4 mM. Glc6P was a competitive inhibitor of Glc1P transport (Ki 0.8 mM), and the two hexose phosphates could exchange with each other, indicating the operation of a single carrier protein. Glc1P/Pi antiport in proteoliposomes showed an exchange stoichiometry at pH 8.0 of 1 mol of phosphate transported per mol of sugar phosphate.

scholarly journals Analysis of a Triose Phosphate/Phosphate Translocator-Deficient Mutant Reveals a Limited Capacity for Starch Synthesis in Rice Leaves

2014 ◽  
Vol 7 (11) ◽  
pp. 1705-1708 ◽  
Author(s):  
Sang-Kyu Lee ◽  
Joon-Seob Eom ◽  
Lars M. Voll ◽  
Christian M. Prasch ◽  
Youn-Il Park ◽  
...  
Keyword(s):  
Starch Synthesis ◽  
Limited Capacity ◽  
Deficient Mutant ◽  
Triose Phosphate ◽  
Phosphate Translocator ◽  
Rice Leaves

scholarly journals Association and release of the major intrinsic membrane glycoprotein from peripheral nerve myelin

1985 ◽  
Vol 228 (1) ◽  
pp. 43-54 ◽  
Author(s):  
J F Poduslo ◽  
J K Yao
Keyword(s):  
Membrane Protein ◽  
Peripheral Nerve ◽  
Gamma Globulin ◽  
Protein A ◽  
Supernatant Fraction ◽  
Radioactive Label ◽  
Lower Phase ◽  
Hydrophobic Domain ◽  
Successive Extraction

Hypo-osmotic homogenization of the endoneurium from the adult-rat sciatic nerve and subsequent evaluation of the 197 000 g aqueous supernatant by sodium dodecyl sulphate pore-gradient electrophoresis (SDS-p.g.e.) revealed a release of the major glycoprotein (P0) (29 000 Mr) from peripheral nerve myelin. Immunological verification of the presence of this asparagine-linked glycoprotein in the aqueous supernatant was obtained by immune overlay after SDS-p.g.e. and electrophoretic transfer to nitrocellulose using anti-P0 gamma-globulin followed by autoradiographic detection with 125I-protein A. A comparison of successive hypo- and iso-osmotic extractions of the endoneurium revealed that the hypo-osmotic extraction released increasing amounts of P0 into the supernatant fraction, whereas the iso-osmotic treatment revealed lower levels of P0 extracted from the myelin and lesser amounts with each successive extraction. Three successive hypo-osmotic extractions resulted in a 2.0-, 2.9-, and 9.5-fold increase in the amount of P0 released compared with the successive iso-osmotic extractions. Although these results suggest that this major myelin glycoprotein has properties similar to those of extrinsic membrane proteins, temperature-dependent phase-partitioning experiments with Triton X-114 revealed that this glycoprotein is recovered in the detergent-enriched lower phase. These results indicate that this major myelin glycoprotein is an amphipathic integral membrane protein with a distinct hydrophobic domain and yet has solubility characteristics typical of an extrinsic membrane protein. P0 labelled in vitro with [3H]mannose could be immunoprecipitated from the aqueous supernatant with anti-P0 gamma-globulin by centrifugation at 197000g without the addition of second antibody or protein A. Analysis of such an immune precipitate after incorporation in vitro with [14C]acetate to label endoneurial lipids revealed that all major endoneurial lipid classes contained radioactive label, as determined by fluorography after high-performance t.l.c. The mechanism of release of this intrinsic glycoprotein from the myelin membrane, therefore, involves the osmotic-dependent formation of mixed micelles or membrane vesicles with endogenous membrane lipids.

scholarly journals ADP-glucose drives starch synthesis in isolated maize endosperm amyloplasts: characterization of starch synthesis and transport properties across the amyloplast envelope

1997 ◽  
Vol 324 (2) ◽  
pp. 503-509 ◽  
Author(s):  
Torsten MÖHLMANN ◽  
Joachim TJADEN ◽  
Gundrun HENRICHS ◽  
Paul W. QUICK ◽  
Rainer HÄUSLER ◽  
...  
Keyword(s):  
Starch Synthesis ◽  
Dihydroxyacetone Phosphate ◽  
Maize Endosperm ◽  
Endosperm Tissue ◽  
Plastid Envelope ◽  
Phosphorylated Compounds ◽  
Saturation Kinetics ◽  
Uptake Data ◽  
Hexose Phosphates

We recently developed a method of purifying amyloplasts from developing maize (Zea mays L.) endosperm tissue [Neuhaus, Thom, Batz and Scheibe (1993) Biochem. J. 296, 395–401]. In the present paper we analyse how glucose 6-phosphate (Glc6P) and other phosphorylated compounds enter the plastid compartment. Using a proteoliposome system in which the plastid envelope membrane proteins are functionally reconstituted, we demonstrate that this type of plastid is able to transport [14C]Glc6P or [32P]Pi in counter exchange with Pi, Glc6P, dihydroxyacetone phosphate and phosphoenolpyruvate. Glucose 1-phosphate, fructose 6-phosphate and ribose 5-phosphate do not act as substrates for counter exchange. Besides hexose phosphates, ADP-glucose (ADPGlc) also acts as a substrate for starch synthesis in isolated maize endosperm amyloplasts. This process exhibits saturation kinetics with increasing concentrations of exogenously supplied [14C]ADPGlc, reaching a maximum at 2 mM. Ultrasonication of isolated amyloplasts greatly reduces the rate of ADPGlc-dependent starch synthesis, indicating that the process is dependent on the intactness of the organelles. The plastid ATP/ADP transporter is not responsible for ADPGlc uptake. Data are presented that indicate that ADPGlc is transported by another translocator in counter exchange with AMP. To analyse the physiology of starch synthesis in more detail, we examined how Glc6P- and ADPGlc-dependent starch synthesis in isolated maize endosperm amyloplasts interact. Glc6P-dependent starch synthesis is not inhibited by increasing concentrations of ADPGlc. In contrast, the rate of ADPGlc-dependent starch synthesis is reduced by increasing concentrations of ATP necessary for Glc6P-dependent starch synthesis. The possible modes of inhibition of ADPGlc-dependent starch synthesis by ATP are discussed with respect to the stromal generation of AMP required for ADPGlc uptake.

scholarly journals The chloroplast import receptor is an integral membrane protein of chloroplast envelope contact sites.

1990 ◽  
Vol 111 (5) ◽  
pp. 1825-1838 ◽  
Author(s):  
D J Schnell ◽  
G Blobel ◽  
D Pain
Keyword(s):  
Membrane Protein ◽  
Protein Import ◽  
Integral Membrane Protein ◽  
Chloroplast Envelope ◽  
Bisphosphate Carboxylase ◽  
Chloroplast Import ◽  
Chloroplast Membrane ◽  
Phosphate Translocator ◽  
Triton X ◽  
Import Receptor

A chloroplast import receptor from pea, previously identified by antiidiotypic antibodies was purified and its primary structure deduced from its cDNA sequence. The protein is a 36-kD integral membrane protein (p36) with eight potential transmembrane segments. Fab prepared from monospecific anti-p36 IgG inhibits the import of the ribulose-1,5-bisphosphate carboxylase small subunit precursor (pS) by interfering with pS binding at the chloroplast surface. Anti-p36 IgGs are able to immunoprecipitate a Triton X-100 soluble p36-pS complex, suggesting a direct interaction between p36 and pS. This immunoprecipitation was specific as it was abolished by a pS synthetic transit peptide, consistent with the transit sequence receptor function of p36. Immunoelectron microscopy localized p36 to regions of the outer chloroplast membrane that are in close contact with the inner chloroplast membrane. Comparison of the deduced sequence of pea p36 to that of other known proteins indicates a striking homology to a protein from spinach chloroplasts that was previously suggested to be the triose phosphate-3-phosphoglycerate-phosphate translocator (phosphate translocator) (Flügge, U. I., K. Fischer, A. Gross, W. Sebald, F. Lottspeich, and C. Eckerskorn. 1989. EMBO (Eur. Mol. Biol. Organ.) J. 8:39-46). However, incubation of Triton X-100 solubilized chloroplast envelope material with hydroxylapatite indicated that p36 was quantitatively absorbed, whereas previous reports have shown that phosphate translocator activity does not bind to hydroxylapatite (Flügge, U. I., and H. W. Heldt. 1981. Biochim. Biophys. Acta. 638:296-304. These data, in addition to the topology and import inhibition data presented in this report support the assignment of p36 as a receptor for chloroplast protein import, and argue against the assignment of the spinach homologue of this protein as the chloroplast phosphate translocator.

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