Bovine galactosyltransferase: identification of a clone by direct immunological screening of a cDNA expression library

Abstract

A 1.3-kilobase cDNA clone (7A) coding for bovine galactosyltransferase (glycoprotein 4-beta-galactosyltransferase, EC 2.4.1.38) was isolated from a lambda gt11 expression library by immunological screening with monospecific polyclonal antisera to the affinity-purified bovine enzyme. The nucleotide sequence of this clone predicts an open reading frame that starts at the 5' end of the insert and codes for a polypeptide of 334 amino acids with Mr 37,645. Based on a Mr of 57,000 for the membrane-bound enzyme this clone accounts for approximately 61% of the coding sequence. Portions of the predicted amino acid sequence matched the six tryptic peptides isolated from affinity-purified bovine galactosyltransferase. Clone 7A hybridizes to a 4.8-kilobase bovine mRNA and identifies multiple EcoRI restriction fragments in bovine, murine, and human DNA.