Evidence for two types of phosphate translocators in sweet-pepper (Capsicum annuum L) fruit chromoplasts

Autor(en): Quick, WP
Neuhaus, HE
Stichwörter: AMYLOPLASTS; Biochemistry & Molecular Biology; CHLOROPLAST ENVELOPE; GLUCOSE-6-PHOSPHATE; INNER MEMBRANE; INORGANIC-PHOSPHATE; PISUM-SATIVUM-L; PLASTIDS; SPINACH-CHLOROPLASTS; STARCH SYNTHESIS; TRANSPORT
Erscheinungsdatum: 1996
Herausgeber: PORTLAND PRESS
Journal: BIOCHEMICAL JOURNAL
Volumen: 320
Ausgabe: 1
Startseite: 7
Seitenende: 10
Zusammenfassung: 
We have investigated whether there is evidence for the presence of different types of phosphate translocators in envelopes purified from pepper-fruit chromoplasts. A method was developed that allowed the purification of envelope membranes from isolated pepper-fruit chromoplasts. Proteoliposomes containing envelope-membrane proteins are able to import inorganic phosphate (P-i) or glucose 6-phosphate (Glc6P). In both cases, the rate of import is strongly dependent upon preloading of proteoliposomes with either P-i, dihydroxyacetone phosphate (DHAP) or Glc6P. This demonstrates the presence of a phosphate translocator activity catalysing a counter exchange of phosphorylated intermediates. Interestingly, a high external concentration of Glc6P does not strongly inhibit P-i uptake into proteoliposomes preloaded with DHAP, whereas external Glc6P strongly inhibits P-i uptake into proteoliposomes preloaded with Glc6P. This observation strongly indicates that two types of phosphate translocator are present in chromoplast envelopes from red-pepper fruits. These data are discussed with respect to the possible physiological function of two types of phosphate translocator in one type of plastid.
ISSN: 02646021

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