The tonoplast-associated citrate binding protein (CBP) of Hevea brasiliensis. Photoaffinity labeling, purification, and cloning of the corresponding gene.
A detailed comparison of citrate uptake into the vacuole-like lutoids of rubber tree (Hevea brasiliensis Muell. Arg.) and of malate and citrate transport into barley (Hordeum vulgare L.) vacuoles revealed very similar transport specificities. In order to identify proteins mediating the transport, two photoreactive analogues (N'-(2-hydroxy-5-azido)-diazo-N-3,5-benzenedicarboxylic acid and 5-azidoisophthalic acid) of malate/citrate were synthesized and found to efficiently inhibit citrate uptake into barley vacuoles (Ki = 18 microM) and Hevea lutoid vesicles (Ki = 27 microM). In vacuoles from both plant species, these photoaffinity probes specifically labeled a single protein with a molecular mass of 23.6 kDa. This citrate binding protein (CBP) was purified to homogeneity from Hevea lutoids, and amino acid sequences were determined for NH2-terminal and tryptic peptides. Using degenerate oligonucleotides of the NH2-terminal sequence, a cDNA coding for the CBP protein of Hevea was isolated. The cDNA codes for a precursor protein of 238 amino acids, containing an NH2-terminal 31-amino acid signal sequence for endoplasmic reticulum targeting, a prerequisite for vacuolar localization. The mature CBP does not show significant sequence similarities to any known primary protein structure and thus represents a member of a novel class of proteins.
Institute of Plant Sciences, Swiss Federal Institute of Technology, Zürich, Switzerland.
D
D
Rentsch
J
J
Görlach
E
E
Vogt
N
N
Amrhein
E
E
Martinoia
D000345:Affinity Labels / Q000378:metabolism / Q000494:pharmacology; D000595:Amino Acid Sequence; D001483:Base Sequence; D001667:Binding, Competitive; D001692:Biological Transport / Q000187:drug effects; D015139:Blotting, Southern; D002264:Carboxylic Acids / Q000494:pharmacology; D002352:Carrier Proteins / Q000096:biosynthesis / Q000302:isolation & purification* / Q000378:metabolism*; D002951:Citrates / Q000378:metabolism*; D003001:Cloning, Molecular; D017931:DNA Primers; D018744:DNA, Plant / Q000302:isolation & purification / Q000378:metabolism; D017343:Genes, Plant; D001467:Hordeum; D007700:Kinetics; D008293:Malates / Q000378:metabolism; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D011487:Protein Conformation; D021382:Protein Sorting Signals / Q000096:biosynthesis / Q000737:chemistry; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism; D015183:Restriction Mapping; D012408:Rubber; D013347:Subcellular Fractions / Q000378:metabolism; D014197:Trees / Q000378:metabolism*; D014617:Vacuoles / Q000378:metabolism
D000345:Affinity Labels; D002264:Carboxylic Acids; D002352:Carrier Proteins; D002951:Citrates; D017931:DNA Primers; D018744:DNA, Plant; D008293:Malates; D021382:Protein Sorting Signals; D011994:Recombinant Proteins; C020723:citrate-binding transport protein; D012408:Rubber