Anti-alpha-1,3-mannosyl-glycoprotein 4-beta-N-acetylglucosaminyltransferase B antibodies are used for the immunodetection of the protein encoded by the MGAT4B gene. In humans, the canonical protein has a reported length of 548 amino acid residues and a mass of 63.2 kDa. Its subcellular localization is in the Golgi. Alternative splicing is reported to yield 3 different isoforms for this protein. It is widely expressed across many tissue types. A member of the Glycosyltransferase 54 protein family, it is a reported glycosyltransferase that catalyzes the transfer of GlcNAc from UDP-GlcNAc to the GlcNAcbeta1-2Manalpha1-3 arm of the core structure of N-linked glycans through a beta1-4 linkage and participates in the production of tri- and tetra-antennary N-linked sugar chains. Other names for this target antigen include GNT-IVB, N-acetylglucosaminyltransferase IVb, N-glycosyl-oligosaccharide-glycoprotein N-acetylglucosaminyltransferase IVb, and GNT-IV. Gene orthologs have been identified in the mouse, rat, bovine, frog, zebrafish, chimpanzee and chicken species.