Review of phosphocholine substituents on bacterial pathogen glycans: Synthesis, structures and interactions with host proteins

•Phosphocholineglycansare distributed throughout the classes of bacterial glycans.•The widespread presence of host proteins capable of reacting with ChoP glycans.•These factors makes the presence of licD genes in other bacteria very striking.•These bacterial ChoPglycans have both positive and negative immune reactivity. Among the non-carbohydrate components of glycans, the addition of phosphocholine (ChoP) to the glycans of pathogens occurs more rarely than acetylation or methylation, but it has far more potent biological consequences. These arise from ChoP's multiple interactions with host proteins, which are important at all stages of the infection process. These stages include initial adherence to cells, encountering the host's innate immune system and then the adaptive immune system. Thus, in the initial stages of an infection, ChoP groups are an asset to the pathogen, but they can turn into a disadvantage subsequently. In this review, we have focussed on structural aspects of these phenomena. We describe the biosynthesis of the ChoP modification, the structures of the pathogen glycans known to carry ChoP groups and the host proteins that recognize ChoP.