Three novel molecular forms of biliary glycoprotein deduced from cDNA clones from a human leukocyte library.

Three cDNA clones that encode three novel variants of biliary glycoprotein a (BGPa), a glycoprotein belonging to the CEA gene family, were identified in a human leukocyte cDNA library. The domain structures of the predicted proteins of the three clones W211, W233 and W239 are N-A1-B1-A2, N-A1-B1 and N-A1-B1-C, respectively; they lack the transmembrane and cytoplasmic domains that exist in the four BGP species (BGPa, BGPb, BGPc and BGPd) previously reported. Their sequences from N to B1 or to A2 are virtually identical to those of BGPa-d. Comparison with the genomic sequence for BGPa-d suggested that these three new BGP variants as well as BGPa-d are generated from the same single gene by alternative splicing of RNA.