Structural determination of oligosaccharides derived from lipooligosaccharide of Neisseria gonorrhoeae F62 by chemical, enzymic, and two-dimensional NMR methods

Abstract

F62 LOS of Neisseria gonorrhoeae consists of two major LOS components; the higher and smaller molecular weight (MW) components were recognized by MAbs 1-1-M and 3F11 respectively. Base-line separation of the two major oligosaccharide (OS) components from F62 LOS was achieved by Bio-Gel P-4 chromatography after dephosphorylation of the OS mixture. The structures of the two major OSs were studied by chemical, enzymatic, and 2D NMR methods [double quantum filtered COSY (DQF-COSY), delayed COSY (D-COSY), homonuclear Hartmann-Hahn spectroscopy (HOHAHA), pure-absorption 2D NOE NMR] as well as methylation followed by GC/MS analysis. The OS component derived from the MAb 1-1-M defined LOS component was determined to have a V3-(beta-N-acetylgalactosaminyl)neolactotetraose structure (GalNAc is beta 1----3-linked to a neolactotetraose) at one of its nonreducing termini as shown below. The above pentaose is linked to a branched diheptose-KDO core in which a GlcNAc is alpha-linked. The OS component derived from the MAb 3F11 defined LOS component did not have a GalNAc residue. The rest of its structure was identical to that of the OS-1, and a neolactotetraose is exposed at its nonreducing terminus. [formula: see text]

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

“…The structure of the LOS of a few strains of GC has been published (1)(2)(3) and is summarized in Fig. 1.…”

“…Fig. 1 A shows the most complete structure that has been reported for strain F62 (1). In the smallest naturally occurring variant, the c~ chain consists ofa lactosyl group (Gal .…”

Structural and Immunochemical Characterization of aNeisseria gonorrhoeae Epitope Defined by a Monoclonal Antibody 2C7; the Antibody Recognizes a Conserved Epitope on Specific Lipo-oligosaccharides in Spite of the Presence of Human Carbohydrate Epitopes

“…In addition to complex LOS expression, studies by us and others (8,11) have shown that gonococci may mimic human glycolipids or may change serum sensitivity by modifying their LOS (15)(16)(17). The 4.5-kDa LOS produced by strain F62 contains a lactoneotetraose moiety that is linked to the Hep [1] residue of the core trisaccharide as described above (11).…”

“…The 4.5-kDa LOS produced by strain F62 contains a lactoneotetraose moiety that is linked to the Hep [1] residue of the core trisaccharide as described above (11). This tetraose is the carbohydrate moiety also found in a human glycosphingolipid, paragloboside (8,11).…”

“…The 4.5-kDa LOS produced by strain F62 contains a lactoneotetraose moiety that is linked to the Hep [1] residue of the core trisaccharide as described above (11). This tetraose is the carbohydrate moiety also found in a human glycosphingolipid, paragloboside (8,11). Furthermore, in vitro experiments showed that gonococci utilize exogenous cytidine monophospho-N-acetylneuraminic acid and sialylate their LOS (17).…”