Isolation and characterization of a cyanobacterium-binding protein and its cell wall receptor in the lichen Peltigera canina

摘要

Peltigera canina, a cyanolichen containing Nostoc as cyano-biont, produces and secretes arginase to a medium containing arginine. Secreted arginase acts as a lectin by binding to the surface of Nostoc cells through a specific receptor which develops urease activity. The enzyme urease has been located in the cell wall of recently isolated cyanobionts. Cytochemical detection of urease is achieved by producing a black, electron-dense precipitate of cobalt sulfide proceeding from CO_2 evolved from urea hydrolysis in the presence of cobalt chloride. This urease has been pre-purified by affinity chromatography on a bead of active agarose to which arginase was attached. Urease was eluted from the beads by 50 mM alpha-D-galactose. The experimentally probedfact that a fungal lectin developing subsidiary arginase activity acts as a recognition factor of compatible algal cells in chloroli-chens can now been expanded to cyanolichens.