The essential endoplasmic reticulum chaperone Rot1 is required for protein N- and O-glycosylation in yeast.

Rot1 is an essential yeast protein originally shown to be implicated in such diverse processes such as β-1,6-glucan synthesis, actin cytoskeleton dynamics, or lysis of autophagic bodies. More recently also a role as a molecular chaperone has been discovered. Here we report that Rot1 interacts in a synthetic manner with ...
Ost3, one of the nine subunits of the oligosaccharyltransferase complex, the key enzyme of N-glycosylation. Deletion of OST3 in the rot1-1 mutant causes a temperature sensitive phenotype as well as sensitivity towards compounds interfering with cell wall biogenesis such as Calcofluor White, caffeine, Congo Red and hygromycin B, whereas deletion of OST6, a functional homolog of OST3, has no effect. Oligosaccharyltransferase activity in vitro determined in membranes from rot1-1ost3 cells was found to be decreased to 45% compared to wild-type membranes, and model glycoproteins of N-glycosylation, like carboxypeptidase CPY, Gas1 or DPAP B, displayed an underglycosylation pattern. By affinity chromatography a physical interaction between Rot1 and Ost3 was demonstrated. Moreover, Rot1 was found to be involved also in the O-mannosylation process, as glycosylation of distinct glycoproteins of this type were affected as well. Altogether the data extend the role of Rot1 as a chaperone required to ensure proper glycosylation.
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Date: Apr. 04, 2012
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