OpsX from Haemophilus influenzae Represents a Novel Type of Heptosyltransferase I in Lipopolysaccharide Biosynthesis

The inner core region of the lipopolysaccharide (LPS) of Haemophilus influenzae is characterized by the presence of a phosphorylated 3-deoxy-α-d-manno-octulosonic acid (Kdo). In this study, we show that the heptosyltransferase I adding the first l-glycero-d-manno-heptose residue to this acceptor is encoded by the gene opsX, which differs in substrate specificity from the other heptosyltransferase I, known as WaaC.