THE TONOPLAST-ASSOCIATED CITRATE BINDING-PROTEIN (CBP) OF HEVEA-BRASILIENSIS - PHOTOAFFINITY-LABELING, PURIFICATION, AND CLONING OF THE CORRESPONDING GENE
D. Rentsch et al., THE TONOPLAST-ASSOCIATED CITRATE BINDING-PROTEIN (CBP) OF HEVEA-BRASILIENSIS - PHOTOAFFINITY-LABELING, PURIFICATION, AND CLONING OF THE CORRESPONDING GENE, The Journal of biological chemistry, 270(51), 1995, pp. 30525-30531
A detailed comparison of citrate uptake into the vacuole like lutoids
of rubber tree (Hevea brasiliensis Muell. Arg,) and of malate and citr
ate transport into barley (Hordeum vulgare L.) vacuoles revealed very
similar transport specificities, In order to identify proteins mediati
ng the transport, two photoreactive analogues 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 upt
ake into barley vacuoles (K-i = 18 mu M) and Hevea lutoid vesicles (K-
i = 27 mu M). 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 homogene
ity from Hevea lutoids, and amino acid sequences were determined for N
H2-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 aci
ds, containing an NH2-terminal 31-amino acid signal sequence for endop
lasmic 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 nove
l class of proteins.