A novel Arabidopsis thaliana protein is a functional peripheral-type benzodiazepine receptor.
A key element in the regulation of mammalian steroid biosynthesis is the 18 kDa peripheral-type benzodiazepine receptor (PBR), which mediates mitochondrial cholesterol import. PBR also possess an affinity to the tetrapyrrole metabolite protoporphyrin. The bacterial homolog to the mammalian PBR, the Rhodobacter TspO (CrtK) protein, was shown to be involved in the bacterial tetrapyrrole metabolism. Looking for a similar mitochondrial import mechanism in plants, protein sequences from Arabidopsis and several other plants were found with significant similarities to the mammalian PBR and to the Rhodobacter TspO protein. A PBR-homologous Arabidopsis sequence was cloned and expressed in E. coli. The recombinant gene product showed specific high affinity benzodiazepine ligand binding. Moreover, the protein applied to E. coli protoplasts caused an equal benzodiazepine-stimulated uptake of cholesterol and protoporphyrin IX. These results suggest that the PBR like protein is involved in steroid import and is directing protoporphyrinogen IX to the mitochondrial site of protoheme formation.
Lindemann
Peter
P
Institut für Pharmazeutische Biologie, Martin-Luther-Universität Halle-Wittenberg, Hoher Weg 8, D-06120 Halle, Germany. lindemann@pharmazie.uni-halle.de
Koch
Antje
A
Degenhardt
Babett
B
Hause
Gerd
G
Grimm
Bernhard
B
Papadopoulos
Vassilios
V
D017360:Arabidopsis / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D001569:Benzodiazepines / Q000378:metabolism; D001667:Binding, Competitive / Q000235:genetics; D002352:Carrier Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D002784:Cholesterol / Q000378:metabolism; D018076:DNA, Complementary / Q000235:genetics / Q000302:isolation & purification; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D019143:Evolution, Molecular; D006418:Heme / Q000096:biosynthesis*; D008024:Ligands; D008854:Microscopy, Electron; D008928:Mitochondria / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure; D008969:Molecular Sequence Data; D010802:Phylogeny; D011524:Protoporphyrins / Q000378:metabolism; D011869:Radioligand Assay; D011963:Receptors, GABA-A / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D013256:Steroids / Q000378:metabolism*
D029681:Arabidopsis Proteins; D002352:Carrier Proteins; D018076:DNA, Complementary; C490040:F17A22.16 protein, Arabidopsis; D008024:Ligands; D011524:Protoporphyrins; D011963:Receptors, GABA-A; D011993:Recombinant Fusion Proteins; D013256:Steroids; D001569:Benzodiazepines; D006418:Heme; D002784:Cholesterol; C028025:protoporphyrin IX