The molecular mechanism of phase variation of H. influenzae lipopolysaccharide

Weiser, Jeffrey N.; Love, Jennifer M.; Moxon, E. Richard

doi:10.1016/0092-8674(89)90011-1

Cited by 300 publications

(257 citation statements)

References 27 publications

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“…A strong correlation exists between the epitopes of H. influ- (26,27). There may, therefore, be modulation of LPS sialylation phenotypes depending on the relative expression levels of both of these genes.…”

Section: Discussionmentioning

confidence: 99%

Identification of a Bifunctional Lipopolysaccharide Sialyltransferase in Haemophilus influenzae

Fox

Cox

Gilbert

et al. 2006

Journal of Biological Chemistry

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The lipopolysaccharide (LPS) of non-typeableHere we describe a second sialyltransferase, Lic3B, that is a close homologue of Lic3A and present in 60% of NTHi isolates tested. A recombinant form of Lic3B was expressed in Escherichia coli and purified by affinity chromatography. We used synthetic fluorescent acceptors with a terminal lactose or sialyllactose to show that Lic3B has both ␣-2,3-and ␣-2,8-sialyltransferase activities. Structural analysis of LPS from lic3B mutant strains of NTHi confirmed that only monosialylated species were detectable, whereas disialylated species were detected upon inactivation of lic3A. Furthermore, introduction of lic3B into a lic3B-deficient strain background resulted in a significant increase in sialylation in the recipient strain. Mass spectrometric analysis of LPS indicated that glycoforms containing two Neu5Ac residues were evident that were not present in the LPS of the parent strain. These findings characterize the activity of a second sialyltransferase in H. influenzae, responsible for the addition of di-sialic acid to the LPS. Modification of the LPS by di-sialylation conferred increased resistance of the organism to the killing effects of normal human serum, as compared with mono-sialylated or non-sialylated species, indicating that this modification has biological significance.

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Section: Discussionmentioning

confidence: 99%

Identification of a Bifunctional Lipopolysaccharide Sialyltransferase in Haemophilus influenzae

Fox

Cox

Gilbert

et al. 2006

Journal of Biological Chemistry

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“…Thus, the conserved presence of lex2 in serotype b strains may contribute to the virulence of these strains, those most frequently causing systemic and meningeal infection (Turk & May, 1967). Organisms contained in the cerebrospinal fluid of newly diagnosed cases of meningitis showed a majority (>99 %) of organisms binding mAb 4C4 compared to only <0?1 % when organisms were cultured in vitro (Weiser et al, 1989b). The importance to the organism of the digalactoside in the globoside extension from HepI might be indicated by the emphasis placed on the switching of its expression.…”

Section: Discussionmentioning

confidence: 99%

The role of lex2 in lipopolysaccharide biosynthesis in Haemophilus influenzae strains RM7004 and RM153

et al. 2003

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The locus lex2, comprising lex2A and lex2B, contributes to the phase-variable expression of lipopolysaccharide (LPS) of Haemophilus influenzae and was found to be present in 74 % of strains investigated. lex2A contains 59-GCAA repeats which vary in number from 4 to 46 copies between strains. The locus was cloned from the serotype b strains RM7004 and RM153 and showed >99 % nucleotide sequence identity between these strains and the published lex2 sequence. Disruption of the lex2B gene in strain RM7004 resulted in truncation of some LPS glycoforms, shown by gel fractionation, with only one glycoform reacting with a digalactosidespecific monoclonal antibody, 4C4, compared with four LPS glycoforms in the more elongated LPS of the parent strain. Mass spectrometry and NMR analyses of LPS from the lex2B mutant revealed loss of the terminal digalactoside as well as the second b-glucose extending from the first heptose of the inner core. The authors conclude that Lex2B is the b-(1-4)-glucosyltransferase that adds the second b-glucose to the first b-glucose as part of the oligosaccharide extension from the first heptose of the LPS of strain RM7004. Investigation of the expression of the lex2 locus indicated that the genes are co-transcribed and that both reading frames are required for addition of this second b-glucose in a phase-variable manner.

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“…The laboratories of Moxon and Hansen (28)(29)(30) have shown that this also occurs in another mucosal pathogen, Haemophilus influenzae, where at least four genes are subject to phase variation. In this organism, the mechanism is also by slipped-strand mispairing due to repeated tetrameric sequences, which can be either CAAT or GCAA.…”

Section: Discussionmentioning

confidence: 99%

Variation of gonococcal lipooligosaccharide structure is due to alterations in poly-G tracts in lgt genes encoding glycosyl transferases.

Yang

Gotschlich

1996

The Journal of Experimental Medicine

116

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SUlTlnlaryThe lipooligosaccharide (LOS) expressed by gonococci spontaneously varies its structure at high frequency, but the underlying genetic mechanism has not been described. We have previously reported that the genes encoding the glycosyl transferases responsible for the biosynthesis of the variable o~ chain of the LOS of Neisseria gonorrhoeae are located in a locus containing five genes, lgtA, lgtB, IgtC, IgtD, and lgtE. Sequence analysis showed that tgtA, lgtC, and IgtD contained poly-G tracts within the coding frames, leading to the hypothesis that shiftsin the number of guanosine residues in the poly-G tracts might be responsible for the.high frequency variation in structure of gonococcal LOS. We now provide experimental evidence confirming this hypothesis.

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The molecular mechanism of phase variation of H. influenzae lipopolysaccharide

Cited by 300 publications

References 27 publications

Identification of a Bifunctional Lipopolysaccharide Sialyltransferase in Haemophilus influenzae

Identification of a Bifunctional Lipopolysaccharide Sialyltransferase in Haemophilus influenzae

The role of lex2 in lipopolysaccharide biosynthesis in Haemophilus influenzae strains RM7004 and RM153

Variation of gonococcal lipooligosaccharide structure is due to alterations in poly-G tracts in lgt genes encoding glycosyl transferases.

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