Features and functions of covalently linked proteins in fungal cell walls

The cell walls of many ascomycetous yeasts consist of an internal network of stress-bearing polysaccharides, which serve as a scaffold for a dense external layer of glycoproteiris. GPI-modified proteins are the most abundant cell wall proteins and often display a common oraanization. Their C-terminus can link them covalently to the polysaccharide network, they possess ail internal serine and threonine-rich spacer domain, and the N-terminal region contains a functional domain. Other proteins bind to the polysaccharide network through a mild-alkali-sensitive linkage. Many cell wall proteins are carbohydrate/glycan-modifying enzymes; adhesion proteins are prominent; proteins involved in iron uptake are present, and also specialized proteins that probably help the fungus to survive in its natural environment. The protein composition of the cell wall depends on environmental conditions and developmental stage. We present evidence that the cell wall of mycelial species of the Ascomycotina, is similarly organized and contains glycoproteins with comparable functions. (c) 2005 Elsevier Inc. All rights reserved.