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Identification of a lipopolysaccharide α‐2,3‐sialyltransferase from Haemophilus influenzae
Author(s) -
Hood Derek W.,
Cox Andrew D.,
Gilbert Michel,
Makepeace Katherine,
Walsh Shan,
Deadman Mary E.,
Cody Alison,
Martin Adele,
Månsson Martin,
Schweda Elke K. H.,
Brisson JeanRobert,
Richards James C.,
Moxon E. Richard,
Wakarchuk Warren W.
Publication year - 2001
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.2001.02204.x
Subject(s) - biology , haemophilus influenzae , microbiology and biotechnology , lipopolysaccharide , identification (biology) , sialyltransferase , virology , haemophilus , bacteria , immunology , genetics , antibiotics , glycoprotein , botany
We have identified a gene for the addition of N‐ acetylneuraminic acid (Neu5Ac) in an α‐2,3‐linkage to a lactosyl acceptor moiety of the lipopolysaccharide (LPS) of the human pathogen Haemophilus influenza e. The gene is one that was identified previously as a phase‐variable gene known as lic3A . Extracts of H. influenzae , as well as recombinant Escherichia coli strains producing Lic3A, demonstrate sialyltransferase activity in assays using synthetic fluorescent acceptors with a terminal galactosyl, lactosyl or N‐ acetyl‐lactosaminyl moiety. In the RM118 strain of H. influenzae , Lic3A activity is modulated by the action of another phase‐variable glycosyltransferase, LgtC, which competes for the same lactosyl acceptor moiety. Structural analysis of LPS from a RM118: lgtC mutant and the non‐typeable strain 486 using mass spectrometry and nuclear magnetic resonance (NMR) spectroscopy confirmed that the major sialylated species has a sialyl‐α‐(2–3)‐lactosyl extension off the distal heptose. This sialylated glycoform was absent in strains containing a lic3A gene disruption. Low amounts of sialylated higher molecular mass glycoforms were present in RM118: lgtC lic3A , indicating the presence of a second sialyltransferase. Lic3A mutants of H. influenzae strains show reduced resistance to the killing effects of normal human serum. Lic3A , encoding an α‐2,3‐sialyltransferase activity, is the first reported phase‐variable sialyltransferase gene.