engleski

Yeast cell wall glycoproteins: detection-structure-function

It has been shown that the PMT gene family is responsible for protein-O-mannosylation in S. cerevisiae and that certain triple pmt disruptions are lethal (1). Other multiple disruptions could be saved, if the cells were osmotically stabilized indicating that protein O-glycosylation is required for cell awll integrity. To understand this phenomenon, it was decided to analyzed and characterized the complete set of yeast cell wall proteins. Using non-permeant biotinylation reagent more than 20 cell surface proteins could be specifically labelled (2). One group of proteins could be extarcted by SDS under reducing conditions, other proteins were covalently linked within the wall and could be devided in those extarctable by glucanases and those which could be released by 30 mM NaOH. After purification and N-terminal sequencing, nine new cell wall components have been identified. Among them were four NaOH extractable proteins, which formed a new family of Pir-proteins (proteins with internal repeats). In order to investigate the role of covalently linked, NaOH-extractable cell wall proteins, genes encoding the four Pir-proteins Ccw5p, Ccw6p, Ccw7p and Ccw8p were disrupted and the phenotype of the mutants optained was examened (3). Besides, three new identified noncovalently linked cell wall proteins were found to be related to glucanases. Single knockouts of this three potential glucanases did not result in dramatic phenotypes, however multiple ones partly did (4). Evidence has been obtained that almost all of these cell wall proteins are O-glycosylated.

cell wall proteins; glycosilation; Pir proteins

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