Abstract
All living cells generate structurally complex and compositionally diverse spectra of glycans and glycoconjugates, critical for organismal evolution, development, functioning, defense, and survival. Glycosyltransferases (GTs) catalyze the glycosylation reaction between activated sugar and acceptor substrate to synthesize a wide variety of glycans. GTs are distributed among more than 130 gene families and are involved in metabolic processes, signal pathways, cell wall polysaccharide biosynthesis, cell development, and growth. Glycosylation mainly takes place in the endoplasmic reticulum (ER) and Golgi, where GTs and glycosidases involved in this process are distributed to different locations of these compartments and sequentially add or cleave various sugars to synthesize the final products of glycosylation. Therefore, delivery of these enzymes to the proper locations, the glycosylation sites, in the cell is essential and involves numerous secretory pathway components. This review presents the current state of knowledge about the mechanisms of protein trafficking between ER and Golgi. It describes what is known about the primary components of protein sorting machinery and trafficking, which are recognition sites on the proteins that are important for their interaction with the critical components of this machinery.
Highlights
All living cells generate structurally complex and compositionally diverse spectra of glycans and glycoconjugates, critical for organismal evolution, development, functioning, defense, and survival
Arginine and Lysine residues are commonly found in most GTs and glycosidases and can directly interact with cargo receptors and COP coatomers
The positive charge and branched structure of the arginine and lysine residues are critical in the protein–protein interactions with the cargo receptors and COP coatomers
Summary
All living cells generate structurally complex and compositionally diverse spectra of glycans and glycoconjugates, critical for organismal evolution, development, functioning, defense, and survival. Glycosylation is the reaction that forms glycosidic linkages between activated sugar (donor substrate) and acceptor substrate (protein, lipid, polysaccharide, etc.) This reaction is performed by a large group of specialized enzymes, called glycosyltransferases, and broadly takes place in most organisms, such as yeast, humans, plants, etc. The first sugar, N-acetylgalactosamine (GalNAc), links to serine and threonine residues in Golgi and is called O-GalNAc. Multiple core sugar sequences are found in O-GalNAc-type glycosylation, and different biosynthesis steps are involved [6,23]. Most GTs involved in synthesizing polysaccharides are integral membrane proteins with multiple TMDs. For example, in plants, cellulose synthases (CESA) [3,26,27,28] are organized in multiprotein cellulose synthase complexes (CSCs) and synthesize cellulose microfibrils. The homogalacturonan synthesizing galacturonosyltransferase (GAUT) 1 and GAUT7 proteins form a heterocomplex required to anchor catalytically active GAUT1 to Golgi [35]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
