engleski

News from the Covalently Linked Cell Wall Protein Ccw5p/Pir4p

A) Pir-Proteins get attached to the yeast cell wall by a transglutaminase-type reaction. Ccw5 is a Pir-protein (Pir4p ; protein with internal repeats), but does contain the typical repetitive sequence only once. A consequence of deleting this sequence is loss of the cell wall bound form of the protein to the medium. Site directed mutagenesis within the sequence showed thet three glutamins and one aspartic acid, not however the two hydroxy amino acids are essential for cell wall linkage. Protein sequence analysis of the wild type protein uncovered the fact that one of the 3 glutamins is attached to cell wall material ; the attached moiety was missing in the protein that is normally found in the medium. These and further results to be discussed strongly suggest that Pir proteins get covalently linked to cell walls by a transglutaminase-type of reaction. B) O-manosylation of Ccw5 controls its N-glycosylation. O-manosylation of secretory proteins are catalyzed by the ER-located DolPman: Protein Mannosyltransferases of the Pmt family (Pmt1-Pmt6). Results will be presented which demonstrate that O-mannosylation prevents N-glycosylation of the Ccw5 protein.

yeast cell wall; cell wall proteins; Pir4; Ccw5

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