Structural characterization of the galactoxylomannan of Cryptococcus neoformans Cap67

Unusual Galactofuranose Modification of a Capsule Polysaccharide in the Pathogenic Yeast Cryptococcus neoformans

“…Early studies of capsule polysaccharides suggested that Galf was a terminal substituent of GXMGal (42,53). The site of this glycosyl modification was never determined, however, so Galf is not included in the currently accepted GXMGal structure (Fig.…”

“…To address this gap in knowledge, we analyzed GXMGal from the C. neoformans serotype D strain CAP67 (strains are listed in supplemental Table S1). We used this strain for structural studies because it does not produce GXM; this simplifies GXMGal purification and reduces potential contamination with the more abundant GXM polysaccharide (31,42,48,54). One-dimensional 13 C NMR analysis of CAP67 GXMGal (data not shown) showed the anomeric signal at 110 ppm that was originally attributed to Galf (42).…”

“…1A) (31,42). Compositional analyses have further suggested that GXMGal contains Galf (42), although neither the site of this modification nor its functional significance has been determined.…”

“…GXMGal, typically ϳ0.1 MDa (38,39), has a backbone of ␣1,6-linked Galp with ␣1,3-Manp-␣1,4-Manp-␤1,3-Galp side chains; the side chain residues are additionally modified with variable amounts of ␤1,2-and ␤1,3-Xylp and ␤1,3-GlcAp (see Fig. 1A) (31,42). Compositional analyses have further suggested that GXMGal contains Galf (42), although neither the site of this modification nor its functional significance has been determined.…”

Functional cloning and characterization of a UDP- glucuronic acid decarboxylase: The pathogenic fungus Cryptococcus neoformans elucidates UDP-xylose synthesis

“…1); this polymer consists of a galactose backbone with trimer side chains of galactose and mannose. Each GalXM side chain bears between one and three xylose residues (7).…”