♦ See referenced article, J. Biol. Chem. 2014, 289, 20405–20420
Protein O-glycosylation in plants is not very well understood. Researchers know that serine residues in a plant cell wall protein are glycosylated with O-galactose. However, the enzyme responsible for the post-translational modification is not known. In this Paper of the Week, a team led by Yoh-ichi Shimma at the National Institute of Advanced Industrial Science and Technology in Japan identified and analyzed the gene family for the serine O-α-galactosyltransferases. The investigators obtained the genes from both the alga Chlamydomonas reinhardtii and the plant Arabidopsis thaliana. From their sequence and other analyses, the investigators concluded that serine O-α-galactosyltransferases are a new class of glycosyltransferases that appear only in plants. They also showed that the enzymes required a hydroxylated proline adjacent to the serine to be O-glycosylated and are localized to the endoplasmic reticulum. The authors say, “The identification of novel glycosyltransferases contributes to elucidation of how protein glycosylation has evolved in plants.”
Schematic diagram of the serine α-galactosyltransferase reaction.