Molecular cloning and functional expression of β1,2‐xylosyltransferase cDNA from Arabidopsis thaliana1

Abstract

The transfer of xylose from UDP‐xylose to the core β‐linked mannose of N‐linked oligosaccharides by β1,2‐xylosyltransferase (XylT) is a widespread feature of plant glycoproteins which renders them immunogenic and allergenic in man. Here, we report the isolation of the Arabidopsis thaliana XylT gene, which contains two introns and encodes a 60.2 kDa protein with a predicted type II transmembrane protein topology typical for Golgi glycosyltransferases. Upon expression of A. thaliana XylT cDNA in the baculovirus/insect cell system, a recombinant protein was produced that exhibited XylT activity in vitro. Furthermore, the recombinant enzyme displayed XylT activity in vivo in the insect cells, as judged by the acquired cross‐reaction of cellular glycoproteins with antibodies against the β1,2‐xylose epitope. The cloned XylT cDNA as well as the recombinant enzyme are essential tools to study the role of β1,2‐xylose in the immunogenicity and allergenicity of plant glycoproteins at the molecular level.