High impact information on WBP1

• The beta and delta subunits of the oligosaccharyltransferase are encoded by the WBP1 and SWP1 genes [1].
• The Saccharomyces cerevisiae oligosaccharyltransferase was purified as a heteroligomeric complex consisting of six subunits (alpha-zeta) having apparent molecular masses of 64 kD (Ost1p), 45 kD (Wbp1p), 34 kD, 30 kD (Swp1p), 16 kD, and 9 kD [2].
• To analyze the role of this motif in yeast, we constructed a SUC2-WBP1 chimera consisting of the coding sequence for the normally secreted glycoprotein invertase fused to the coding sequence of the COOH terminus (including the transmembrane domain and 16-amino acid cytoplasmic tail) of Wbplp [3].
• Subcellular fractionation revealed that > 90% of the alpha 1,6 mannose-modified fusion protein colocalized with the ER (Wbp1p) and not with the Golgi Och1p-containing compartment or other membrane fractions [3].
• The Saccharomyces cerevisiae Wbp1 protein is an endoplasmic reticulum (ER), type I transmembrane protein which contains a cytoplasmic dilysine (KKXX) motif [3].

Biological context of WBP1

• Four essential gene products, Ost1p, Wbp1p, Swp1p, and Stt3p were shown to be cross-linked to each other in a pairwise fashion [4].
• We show that a combination of kar2 and wbp1 mutations results in a synthetic phenotype with a strongly reduced growth rate at the permissive temperature [5].
• The genetic interaction of kar2 and wbp1 mutations. Distinct functions of binding protein BiP and N-linked glycosylation in the processing pathway of secreted proteins in Saccharomyces cerevisiae [5].
• The 60/62 component represents differentially glycosylated forms of a protein that has sequence homology to ribophorin I. Wbp1p and Swp1p reveal homology to mammalian OST 48 and ribophorin II, respectively [6].

Anatomical context of WBP1

• In addition, in vitro N-glycosylation of the acceptor peptide Tyr-Asn-Leu-Thr-Ser-Val using microsomal membranes from WBP1 depleted cells is reduced as compared with membranes from wild-type cells [7].
• In contrast to results with alpha-COP mutants, we found that Emp47p was mislocalised to the vacuole in mutants affecting beta'-, gamma-, delta-, and zeta-COP subunits of coatomer and that the mutant coatomer bound neither to the Emp47p nor to the Wbp1p di-lysine signal in vitro [8].

Associations of WBP1 with chemical compounds

• Carbohydrate analysis of the invertase-Wbp1 fusion protein using mannose linkage-specific antiserum demonstrated that the fusion protein was efficiently modified by the early Golgi initial alpha 1,6 mannosyltransferase (Och1p) [3].
• An octapeptide corresponding to the C-terminal tail of Wbp1p, a component of the yeast N-oligosaccharyltransferase complex, has been synthesized with a photoreactive phenylalanine at position -5 and was radioactively labeled with [125I]iodine at a tyrosine residue introduced at the N terminus of the peptide [9].

Physical interactions of WBP1

• The OT subunit Wbp1p was found to interact very strongly with Sec61p and Sbh1p and weakly with Sss1p [10].

Other interactions of WBP1

• Depletion of WBP1 correlates with a defect in transferring core oligosaccharides to carboxypeptidase Y and proteinase A in vivo [7].
• Reporter molecules were constructed by replacing parts of a control invertase-Wbp1p chimera with those of Emp24p, and their transport rates were assessed [11].

Analytical, diagnostic and therapeutic context of WBP1

• Immunoprecipitation experiments show that Wbp1p mutated in these two ways is not incorporated into the OT complex [12].

References