RETINOL-BINDING PROTEIN 5; RBP5

Alternative titles; symbols

• CELLULAR RETINOL-BINDING PROTEIN 3; CRBP3
• CRBPIII

HGNC Approved Gene Symbol: RBP5

Cytogenetic location: 12p13.31 Genomic coordinates (GRCh38): 12:7,119,105-7,130,271 (from NCBI)

▼ Cloning and Expression
By EST database analysis using a bovine protein copurified with RBP1 (180260) as query, followed by PCR, Folli et al. (2001) cloned RBP5, which they called CRBPIII. The deduced 135-amino acid protein has a calculated molecular mass of 15.9 kD and shares 55.6% and 49.6% amino acid identity with RBP1 and RBP2 (180280), respectively. RNA dot-blot analysis of human tissues detected strong expression of RBP5 in adult kidney and liver with weak expression in fetal spleen, adult spleen, lymph node, appendix, fetal liver, and fetal kidney. Comparison of hybridization signals showed that RBP5 transcript levels in kidney and liver exceeded those of RBP1 by approximately 200 and 13 times, respectively.

▼ Gene Function
By UV absorption and fluorescence spectroscopy, Folli et al. (2001) showed that RBP5 bound all-trans retinol, and they suggested that RBP5 binds the retinol ligand with a specific interaction similar to that observed in the retinol-RBP1 complex. They estimated a binding of 0.66 mol of retinol ligand per mol of RBP5 and apparent Kd of 60 nM.

▼ Biochemical Features
Crystal Structure

Folli et al. (2001) reported the crystal structure of RBP5 at 2.3-angstrom resolution and observed that it is similar to the RBP1 and RBP2 x-ray models. X-ray diffraction data supported the identification of 2 RBP5 molecules as the asymmetric unit.