Molecular cloning and chromosomal localization of human 4-β-galactosyltransferase

A cDNA clone to human 4-β-galactosyltransferase (EC 2.4.1.38) was isolated from a human liver λgt11 expression library by using a monospecific polyclonal antiserum to affinity-purified bovine enzyme. The authenticity of this cDNA clone has been demonstrated by several criteria. Under conditions of chronic treatment with the β-adrenergic receptor agonist isoproterenol, rat parotid glands show an approximately 10-fold increase in 4-β-galactosyltransferase activity. The increased enzyme activity was reflected in dot-blot analysis of control and isoproterenol-treated rat parotid RNA by using the human cDNA as probe. Hybrid-selection and in vitro translation identified a protein product with a molecular mass of 47 kDa that was immunoprecipitated with the bovine antiserum. The full-length human cDNA clone was then isolated and the DNA sequence for the NH₂-terminal portion of the protein was deduced. Comparison of the NH₂-terminal protein sequence from the bovine protein with that of the human cDNA clone confirmed its identity. In addition, the human cDNA clone was used to localize the gene for 4-β-galactosyltransferase to human chromosome 4 by Southern analysis of a somatic cell hybrid panel.