Cloning and characterization of PRAX-1. A new protein that specifically interacts with the peripheral benzodiazepine receptor

J Biol Chem. 1999 Jan 29;274(5):2938-52. doi: 10.1074/jbc.274.5.2938.


Using a cytoplasmic domain of the peripheral benzodiazepine receptor (PBR) as a bait in the yeast two-hybrid system, we have isolated a cDNA encoding a new protein that specifically interacts with PBR. We named it PRAX-1, for peripheral benzodiazepine receptor-associated protein 1. PRAX-1 is a 1857-amino acid protein, the sequence of which was structurally unrelated to any known proteins. The gene encoding PRAX-1 is located in the q22-q23 region of the long arm of the human chromosome 17. The PRAX-1 mRNA is 7.5 kilobase pairs, predominantly expressed in the central nervous system, pituitary gland, and thymus. At the protein level, we found the PRAX-1 as a single 220-250-kDa protein in the brain and in many different human cell lines tested using specific antibody raised against PRAX-1. Parallel analysis of the PRAX-1 mRNA and protein expression performed in mouse and rat gave similar results. Immunocytochemistry analysis carried out to define the distribution of the PRAX-1 protein in the rat brain showed that PRAX-1 was prevalent in the mesolimbic system, specially abundant in the CA1 subfield of the hippocampus. Exhibiting several domains involved in protein-protein interaction (three proline-rich domains, three leucine-zipper motifs, and an Src homology region 3-like domain), the PRAX-1 may be looked upon as a new adaptator protein. We show that both the Src homology region 3-like domain and a proline-rich domain in PRAX-1 are required for the interaction with PBR. PRAX-1 is a cytoplasmic protein that also partially colocalizes with PBR in the mitochondria, as determined by confocal microscopy and Western blotting. Altogether our observations support a model of interaction implicating PBR and this newly described protein, PRAX-1. As being the first cytoplasmic protein associated with PBR, PRAX-1 is a new tool that opens new fields for exploring PBR biological roles.

MeSH terms

  • Adaptor Proteins, Signal Transducing*
  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • Blotting, Western
  • Brain / metabolism
  • Carrier Proteins / genetics*
  • Carrier Proteins / metabolism*
  • Chickens
  • Chromosome Banding
  • Chromosomes, Human, Pair 17*
  • Cloning, Molecular
  • Consensus Sequence
  • Humans
  • In Situ Hybridization, Fluorescence
  • Mice
  • Molecular Sequence Data
  • RNA, Messenger / metabolism
  • Rats
  • Receptors, GABA-A / metabolism*


  • Adaptor Proteins, Signal Transducing
  • Carrier Proteins
  • RNA, Messenger
  • Receptors, GABA-A
  • TSPOAP1 protein, human

Associated data

  • GENBANK/AF039571