Figure 6. O-linked glycosylation of flagellar proteins in H. pylori. (A) Pseudaminic acid (PseAc) is synthesized in a five-step enzymatic process from a UDP-GlcNAc precursor. The structure of PseAc is shown (inset). It is then linked to a CMP nucleotide donor by PseF, and transferred by PseE from this donor to a serine or threonine residue on a FlaA or FlaB protein before the protein folds. (B) Glycosylated FlaA and FlaB proteins fold in the cytoplasm and display surface-exposed PseAc residues. Modified FlaA and FlaB are then translocated through the flagellar machinery to compose the flagellar filament. PseAc additions are apparent on both proteins within the filament.