Galactomannoproteins of Aspergillus fumigatus

Abstract

Galactofuranose-containing molecules have been repeatedly shown to be important antigens among human fungal pathogens, including Aspergillus fumigatus. Immunogenic galactofuran determinants have been poorly characterized chemically, however. We reported here the characterization of two glycoproteins of A. fumigatus with an N-glycan containing galactofuranose. These proteins are a phospholipase C and a phytase. Chemical characterization of the N-glycan indicates that it is a mixture of Hex 5-13 HexNAc 2 oligosaccharides, the major molecular species corresponding to Hex 6-8 HexNAc 2 . The N-glycan contained one galactofuranose unit that was in a terminal nonreducing position attached to the 2 position of Man. This single terminal nonreducing galactofuranose is essential for the immunoreactivity of the N-glycans assessed either with a monoclonal antibody that recognizes a tetra-␤-1,5-galactofuran chain of galactomannan or with Aspergillus-infected patient sera.

Biosynthesis of the Fungal Cell Wall Polysaccharide Galactomannan Requires Intraluminal GDP-mannose

“…Samples from ⌬glfB were negative at all concentrations. The very low signal observed with fractions from the ⌬gmtA mutant may reflect an extremely limited synthesis of galactomannan (less than 0.1%) due to the "leakiness" of the Golgi toward GDP-Man or be due to contamination by galactofuranosylated glycoproteins that are also recognized by the EB-A2 antibody (44). Together, these data clearly establish a FIGURE 4.…”

Analysis of protein glycosylation by mass spectrometry

“…After a-galactosidase treatment, the MALDI-TOF-MS spectrum of the N-glycans (Fig. 10b) 6 ). Therefore, the N-glycans were efficiently de-galactosylated, indicating that the Gal residues were in normal â-linkages.…”

“…1). This robust and highly sensitive mass spectrometric approach for characterizing the glycosylation pattern of proteins, cells, tissues and physiological fluids allows a rapid characterization of the glycoforms as well as their relative quantitation [5][6][7][8][9][10] .…”

Nonribosomal cyclic peptides: specific markers of fungal infections

“…5,15 None of the assays has performed well enough to be able to recommend its routine use in a clinical laboratory. Higher sensitivity and specificity are obtained in detection of the galactomannan polysaccharide antigen, a cell wall component of Aspergillus, 16 although the high rate of false-positive results has dampened enthusiasm. 17 Another promising antigen molecule is (1 !…”