Complex-type biantennary N-glycans of recombinant human transferrin from Trichoplusia ni insect cells expressing mammalian [beta]-1,4-galactosyltransferase and [beta]-1,2-N-acetylglucosaminyltransferase II

A novel recombinant baculovirus expression vector was used to produce His-tagged human transferrin in a transformed insect cell line (Tn5beta4GalT) that constitutively expresses a mammalian beta-1,4-galactosyltransferase. This virus encoded the His-tagged human transferrin protein in conventional fashion under the control of the very late polyhedrin promoter. In addition, to enhance the synthesis of galactosylated biantennary N-glycans, this virus encoded human beta-1,2- N-acetylglucosaminyltransferase II under the control of an immediate-early (ie1) promoter. Detailed analyses by MALDI-TOF MS, exoglycosidase digestion, and two-dimensional HPLC revealed that the N-glycans on the purified recombinant human transferrin produced by this virus-host system included four different fully galactosylated, biantennary, complex-type glycans. Thus, this study describes a novel baculovirus-host system, which can be used to produce a recombinant glycoprotein with fully galactosylated, biantennary N-glycans.