Structural analysis of milk and testis beta-1,4-galactosyltransferase gene products.

There seems to exist a relatively low similarity between the amino acid sequences of the testis and milk beta-1,4-galactosyltransferase gene products. However, the predicted higher structures of testis and milk beta-1,4-galactosyltransferase proteins revealed a highly significant similarity in the regions required for enzymatic activities. Testis beta-1,4-galactosyltransferase protein contained a WD repeat similar to the motif of the G protein beta subunit type I and a Zn-finger motif at the N- and C-terminal portions of the protein, respectively. Phylogenetic analysis of glycosyltransferase proteins revealed that the ancestral gene of testis and milk beta-1,4-galactosyltransferases and alpha-1,3-galactosyltransferase evolved into three different destinations at about the same time on an evolutionary scale.