Fig. 2.

Glycoengineering approach to the production of glycoconjugate vaccines. An E. coli cell is transformed with three plasmids to generate the glycoconjugate protein (GP). PGCT occurs in three stages: stage 1; Glycan expression, stage 2; Carrier protein design and expression, stage 3; Coupling. The polysaccharide is synthesised on an undecaprenol pyrophosphate lipid anchor (blue/black circle) within the cytoplasm; this is transferred to the periplasmic compartment where PglB recognises the lipid linked reducing end sugar and transfers the polysaccharide en bloc onto an acceptor-sequon (D/E-X-N-X-S/T) on the carrier protein to produce the GP. IM, inner membrane; OM, outer membrane. This figure is adapted from Cuccui et al.⁷⁰