Page 104 - 74_03

Á. PÉREZ CABO y C. GARCÍA MENDOZA AN. R. ACAD. NAC. FARM.

precipitation and ion-exchange chromatography and their respective
characterizations performed as previously described (5, 12).
Hemagglutination inhibition procedure was used for comparative
carbohydrate specificity determination of both lectins (5).

RESULTS AND DISCUSSION

A. bisporus and P. ostreatus lectins purified and characterized
as previously reported (5, 12) have shown that both molecules
are structurally distinct glycoproteins, the former constituting
a tetramer and the latter being dimeric in nature, accounting
their respective monomer molecular masses for 16014 m/z and
44270 m/z. Comparison of the sugar binding specificities
of the two lectins studied by hemagglutination inhibition assays
is exhibited in Table I. Most of the neutral sugars tested had no
effect, except for the galactose at different concentration in each
case. N-acetylgalactosamine also showed a distinct degree of the
hemagglutination inhibition, being more significant with the P.
ostreatus lectin. However purified V. fungicola glucogalactomannan
behaved rather similarly against both lectins, and was even a little
more effective when the same glucogalactomannan was isolated from
cell walls of phrocloraz-Mn pretreated V. fungicola mycelium. This
effect can be explained by the increase of the terminal galactose
residues of the molecule caused by the fungicide (14).

The carbohydrate-protein interaction appears to be due to the
terminal galactose linked at (1-4) to the (1-6) mannose bone of
the V. fungicola glucogalactomannan molecule (5) in which, the
importance of the similar position of the axial C-3 and C-4 hydroxyl
groups of the monosaccharide linked to the galactose molecule was
previously demonstrated by conformational analysis (15). The fact
that this glucogalactomannan behaves as a specific complementary
molecule for both lectins could explain the same mechanism of
recognition and binding of such specific molecules —«target
molecules»— in this disease, as well as the absence of verticillium
disease on the A. bisporus vegetative mycelial phase due to the lack
of lectin (5).

382