| First Author | Tabunoki H | Year | 2002 |
| Journal | J Biol Chem | Volume | 277 |
| Issue | 35 | Pages | 32133-40 |
| PubMed ID | 12052833 | Mgi Jnum | J:78779 |
| Mgi Id | MGI:2386146 | Doi | 10.1074/jbc.M204507200 |
| Citation | Tabunoki H, et al. (2002) Isolation, characterization, and cDNA sequence of a carotenoid binding protein from the silk gland of Bombyx mori larvae. J Biol Chem 277(35):32133-40 |
| abstractText | A carotenoid binding protein (CBP) has been isolated from the silk glands of Bombyx mori larvae. The protein has an apparent molecular mass of 33 kDa and binds carotenoids in a 1:1 molar ratio. Lutein accounts for 90% of the bound carotenoids, whereas alpha-carotene and beta-carotene are minor components. Immunological analysis demonstrated the presence of CBP only in the yellow-colored tissues of the silk gland, midgut, testis, and ovary. Several phenotypes of B. mori mutants linked to carotenoid transport have been utilized to characterize CBP. The Y (yellow hemolymph) gene controls uptake of carotenoids from the midgut lumen into the midgut epithelium, and larvae with the +(Y) gene lack this property. Immunoblotting analysis confirmed the presence of CBP in mutants with the dominant Y gene only. Immunohistochemistry verified the localization of CBP in the villi of the midgut epithelium, indicating that CBP might be involved in absorption of carotenoids. A cDNA clone for CBP encoding a protein of 297 amino acids has been isolated from the B. mori silk gland cDNA library. The deduced amino acid sequence revealed that CBP is a novel member of the steroidogenic acute regulatory (StAR) protein family with its unique structural feature of a StAR-related lipid transfer domain, known to aid in lipid transfer and recognition. Lutein-binding capacity of the recombinant CBP (rCBP) determined by incubating rCBP with lutein followed by immunoprecipitation using anti-CBP IgG conjugated to protein A-Sepharose, demonstrated the formation of a lutein-rCBP complex. Sequence analyses coupled with binding specificity suggest that CBP is a new member of the StAR protein family that binds carotenoids rather than cholesterol. |
