High impact information on OST3

• Here we show that genomes of most multicellular eukaryotes encode two homologs of Stt3p and mammals express two homologs of Ost3p [1].
• Compared to the previously characterized ost1-1 mutant in the oligosaccharyltransferase, and the alg5 mutant in the oligosaccharide assembly pathway, ost3 null mutant yeast appear to be selectively impaired in the glycosylation of several membrane glycoproteins [2].
• Nonetheless, detergent extracts prepared from ost3 null mutant membranes are twofold less active than extracts prepared from wild-type membranes in an in vitro oligosaccharyltransferase assay [2].
• We found that Ost2p and Stt3p have only their N terminus located in the cytosol, whereas Ost3p and Swp1p have only their C terminus oriented in the cytosol [3].
• The residues critical for the OT activity and the stability of Stt3p-Ost4p-Ost3p subcomplex are located in helix alpha2, the larger cytosolic half of this kinked helix [4].

Biological context of OST3

• Disruption of OST6 or OST3 causes only a minor defect in N-glycosylation, but an Deltaost3Deltaost6 double mutant displays a synthetic phenotype, leading to a severe underglycosylation of soluble and membrane-bound glycoproteins in vivo and to a reduced OST activity in vitro [5].

Anatomical context of OST3

• These findings suggest that a localized region of the putative transmembrane domain of Ost4p mediates in stabilization of the interaction with the two other OT subunits (Ost3p and Stt3p) in a subcomplex in the endoplasmic reticulum membrane [6].

Associations of OST3 with chemical compounds

• By blue native polyacrylamide electrophoresis we show that yeast OST consists of two isoforms with distinct functions differing only in the presence of the two related Ost3 and Ost6p proteins [7].

Other interactions of OST3

• In this study we report the identification and functional characterization of a new OST gene, designated OST6, that has homology to OST3 and in particular a strikingly similar membrane topology [5].
• The highly conserved Stt3 protein is a subunit of the yeast oligosaccharyltransferase and forms a subcomplex with Ost3p and Ost4p [8].

Analytical, diagnostic and therapeutic context of OST3

• In addition, using immunoprecipitation techniques and Western blot analysis, we found that with these mutations the interaction between Ost4p, Ost3p, and Stt3p was disrupted [6].

References