Bacterial Protein Glycosylation

Abstract

Protein glycosylation is a common posttranslational modification (ptm) in bacteria, and is frequently found among secreted and cell-surface-associated proteins. Interestingly, several virulence factors among pathogenic bacteria such as flagella and type IV pili are made of glycoproteins, and some glycoproteins function as adhesins and proteases. Remarkably, both N- and O-linked glycoproteins, have been found in bacteria. Protein N-glycosylation has only been reported in a few Gram-negative bacteria, and it is homologous to its eukaryotic counterpart. In contrast, O-glycosylation is more widespread among both Gram-negative and Gram-positive bacteria. Greater details of the glycosylation mechanisms and the functions of the glycan moieties are beginning to be understood. Studies have indicated that bacteria employ diverse mechanisms to O-glycosylate targeted proteins. These mechanisms are different with respect to enzymes that transfer glycan to protein, the nature of sugar donors, the protein acceptors, and the subcellular location of the glycosylation reaction. Interestingly, it has been shown that it is possible to reconstitute different protein glycosylation systems in Escherichia coli, which facilitated the characterization of these systems in the simpler model organism. Bacteria constitute ideal toolboxes for glycoengineering a variety of novel glycan-based vaccines and therapeutics. This chapter focuses on the diverse bacterial glycosylation pathways described and their promising applications in biotechnology.