Document Detail


Ion channel properties of the reconstituted chloroplast triose phosphate/phosphate translocator.
MedLine Citation:
PMID:  7525584     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
The chloroplast triose phosphate/phosphate translocator (cTPT) was isolated from envelope membranes or from transformed yeast cells and reconstituted into artificial membranes. Ionic currents mediated by the cTPT across these membranes were investigated by flux measurements and by the patch-clamp technique. The results of the flux measurements indicate that inorganic phosphate (Pi) at saturating concentrations on both sides of the membrane and chloride (Cl-) at all applied concentrations are transported by the cTPT at rates about 20-fold higher than those measured in intact chloroplasts. After reconstitution of the protein into giant liposomes, single channel currents mediated by the cTPT were resolved with the patch-clamp technique. The protein was shown to be a voltage-dependent anion channel with complex gating revealing sublevels with conductances of 12, 54, 96, and 138 pS for Cl- and 6 pS and 18 pS for Pi, respectively. Recordings from patches compromising multiple channels show a synchronously appearing non-linear current voltage (I/V) relationship in symmetrical buffers, and a different gating at positive and negative membrane potentials. This suggests that the cTPT is incorporated into the membrane in a unidirectional orientation. 3-Phosphoglycerate, a high affinity substrate of the transporter protein, induced a reversible flickering of open channel, and the channel open probability was decreased 60%. It is concluded that, besides its normal counter-exchange mode, the cTPT can also work as a voltage-dependent anion selective channel.
Authors:
M Schwarz; A Gross; T Steinkamp; U I Flügge; R Wagner
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The Journal of biological chemistry     Volume:  269     ISSN:  0021-9258     ISO Abbreviation:  J. Biol. Chem.     Publication Date:  1994 Nov 
Date Detail:
Created Date:  1994-12-28     Completed Date:  1994-12-28     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  2985121R     Medline TA:  J Biol Chem     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  29481-9     Citation Subset:  IM    
Affiliation:
Fachbereich Biologie/Chemie, Universität Osnabrück, Federal Republic of Germany.
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MeSH Terms
Descriptor/Qualifier:
4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / pharmacology
Biological Transport
Chloroplasts / physiology*
Glyceric Acids / pharmacology
Ion Channel Gating
Ion Channels / drug effects,  physiology*
Liposomes
Membrane Proteins / drug effects,  physiology*
Membrane Transport Proteins*
Plant Proteins / drug effects,  physiology*
Spinacia oleracea
Chemical
Reg. No./Substance:
0/Glyceric Acids; 0/Ion Channels; 0/Liposomes; 0/Membrane Proteins; 0/Membrane Transport Proteins; 0/Plant Proteins; 0/TPT protein, plant; 53005-05-3/4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; 820-11-1/3-phosphoglycerate

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