Purification, primary structure characterization, and cellular distribution of two forms of cellular retinol-binding protein, type II from adult small intestine

Cellular retinol-binding protein type II (CRBP(II)) is a major protein in the small intestine, accounting for more than 1% of the soluble protein recovered from rat jujunal mucosa. Two forms of the protein, called CRBP(II)A and CRBP(II)B, were purified from rat small intestine using a three-column procedure. The two forms were present in equal abundance. The primary structures of CRBP(II)A and CRBP(II)B were determined using a combination of techniques including amino acid composition and sequence analyses, and fast atom bombardment and gas chromatography-electron impact mass spectrometry. The results provide a basis for investigating the possibility of different roles of CRBP(II)A and CRBP(II)B within cells, as well as the importance of acetylation of the amino terminus for these biological functions.