T. Fontaine et al., Molecular organization of the alkali-insoluble fraction of Aspergillus fumigatus cell wall, J BIOL CHEM, 275(36), 2000, pp. 27594-27607
Physical and biological properties of the fungal cell wall are determined b
y the composition and arrangement of the structural polysaccharides. Cell w
all polymers of fungi are classically divided into two groups depending on
their solubility in hot alkali. We have analyaed the alkali-insoluble fract
ion of the Aspergillus fumigatus cell wall, which is the fraction believed
to be responsible for fungal cell wall rigidity. Using enzymatic digestions
with recombinant endo-beta-1,3-glucanase and chitinase, fractionation by g
el filtration, affinity chromatography with immobilized lectins, and high p
erformance liquid chromatography, Several fractions that contained specific
interpolysaccharide covalent linkages were isolated. Unique features of th
e A. fumigatus cell wall are (i) the absence of beta-1,6-glucan and (ii) th
e presence of a linear beta-1,3/1,4-glucan, never previously described in f
ungi. Galactomannan, chitin, and beta-1,3-glucan were also found in the alk
ali-insoluble fraction. The beta-1,3-glucan is a branched polymer with 4% o
f beta-1,6 branch points. Chitin, galactomannan, and the Linear beta-1,3/1,
4-glucan were covalently linked to the nonreducing end of beta-1,3-glucan s
ide chains. As in Saccharomyces cerevisiae, chitin was linked via a beta-1,
4 linkage to beta-1,3-glucan. The data obtained suggested that the branchin
g of beta-1,3-glucan is an early event in the construction of the cell wall
, resulting in an increase of potential acceptor sites for chitin, galactom
annan, and the linear beta-1,3/1,4-glucan.