Concanavalin A binds to a mannose-containing ligand in the cell wall of some lichen phycobionts

Concanavalin A, the lectin from Canavalia ensiformis, develops arginase activity depending on Mn2+. The cation cannot be substituted by Ca2+ which, in addition, inhibits Mn2+-supported activity. Fluorescein-labeled Concanavalin A is able to bind to the cell wall of algal cells recently isolated from Evernia prunastri and Xanthoria parietina thalli. This binding involves a ligand, probably a glycoprotein containing mannose, which can be isolated by affinity chromatography. Analysis by SDS-PAGE reveals that the ligand is a dimeric protein composed by two monomers of 54 and 48 kDa. This ligand shows to be different from the receptor for natural lichen lectins, previously identified as a polygalactosylated urease.