Occurrence of poly- N-acetyllactosamine synthesis in Sf-9 cells upon transfection of individual human β-1,4-galactosyltransferase I, II, III, IV, V and VI cDNAs

Abstract

Lectin blot analysis of membrane glycoprotein samples from Sf-9 cells upon transfection of individual human β-1,4-galactosyltransferase (β-1,4-GalT) I, II, III, IV, V et VI cDNAs showed that the endogenous N-linked oligosaccharides are galactosylated (Guo et al., Glycobiology (2001), in press). Further analysis revealed that membrane glycoprotein samples from all the gene-transfected cells are also reactive to Lycopersicon esculentum agglutinin (LEA) et Datura stramonium agglutinin (DSA), both of which bind to oligosaccharides with poly- N-acetyllactosamine chains while no lectin reactive protein bands are detected when blots are pretreated with a mixture of diplococcal β-1,4-galactosidase et jack bean β- N-acetylhexosaminidase or N-glycanase. Analysis of endo-β-galactosidase-digestion products revealed the presence of the Gal1→GlcNAc1→Gal and/or GlcNAc1→Gal structures in the gene-transfected cells. When the homogenates of the gene-transfected cells were used as enzyme sources towards oligosaccharides with the GlcNAcβ1→(3Galβ1→4GlcNAc) 1-3 structures, human recombinant β-1,4-GalTs I et II galactosylated these oligosaccharides more effectively than other β-1,4-GalTs. These results indicate that β-1,4-GalTs I-VI can synthesize poly- N-acetyllactosamine chains with β-1,3- N-acetylglucosaminyltransferase.