Cloning and in vivo expression of functional triose phosphate/phosphate translocators from C₃‐ and C₄‐plants: evidence for the putative participation of specific amino acid residues in the recognition of phosphoenolpyruvate

Abstract

The primary sequences of the chloroplast triose phosphate/phosphate translocator precursor proteins from C4-plants (maize mesophyll cells and Flaveria trinervia) and from the C3-type Flaveria pringlei were determined. The mature parts of these translocators possess 83-94% identical amino acid residues. The C4-translocator protein can be correctly targeted to C3-type chloroplasts and inserted into the envelope membrane. Expression of the mature parts of these chloroplast translocators (cTPT) in transformed yeast cells and subsequent reconstitution of the functional proteins reveals the difference between the recombinant translocator proteins from the two cell types with respect to the transport of phosphoenolpyruvate. Comparison of the cTPT sequences from F. pringlei and F. trinervia in combination with computer-aided molecular modelling of the substrate translocation pore leads to the suggestion, that only minor exchanges of amino acid residues between the C3- and C4-translocator proteins are sufficient to extend their substrate specificities to recognize also phosphoenolpyruvate.

A Chloroplast Phosphate Transporter, PHT2;1, Influences Allocation of Phosphate within the Plant and Phosphate-Starvation Responses

“…However, a program designed specifically to identify chloroplast proteins (ChloroP 1.1) predicted correctly that the TPTs are located in the chloroplast envelope and predicts transit peptide cleavage sites that match those derived experimentally (Fischer et al, 1994). The same analysis applied to PHT2;1 predicted cleavage resulting in a transit peptide of 71 amino acids.…”

The Arabidopsis Thylakoid ADP/ATP Carrier TAAC Has an Additional Role in Supplying Plastidic Phosphoadenosine 5′-Phosphosulfate to the Cytosol

“…Reconstitution of the transport activity was performed essentially as described by Fischer et al (1994) with slight modifications. Liposomes were prepared from acetone-washed phosphatidylcholine (120 to 130 mg mL 21 ) by sonication for 2 min on ice in 100 mM potassium phosphate, pH 7.8, 50 mM potassium gluconate, and 10 mM of substrate as indicated.…”

Genes and Proteins for Solute Transport and Sensing

“…They exchange inorganic phosphate or phosphorylated C3 and C6 compounds. Whereas the triose phosphate/phosphate translocator TPT (Flügge et al, 1989;Fischer et al, 1994) is predominantly active in photosynthetically active tissues, the phosphoenolpyruvate/phosphate translocator (PPT) appears to be ubiquitously expressed and mediates plastidic phosphoenolpyruvate import, which is used as a substrate for the formation of aromatic amino acids via the shikimic acid pathway leading to a series of secondary compounds . The Glc-6-P/phosphate translocator (GPT) is found in heterotrophic tissues, transports both Glc-6-P and triose phosphates, which are used either for the syntheses of starch and fatty acids or is fed into the plastidic oxidative pentose phosphate pathway (Kammerer et al, 1998).…”