Separation and characterization of two alpha 1,2-mannosyltransferase activities from Saccharomyces cerevisiae

Lewis, M.; Ballou, Clinton E.

doi:10.1016/s0021-9258(18)92970-4

Cited by 25 publications

(2 citation statements)

References 32 publications

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“…The question marks indicate the possibility that the complexes contain further enzymes in addition to the proteins described here. Those N-linked glycoproteins that are not hypermannosylated may simply not be substrates for the Van1p-Mnn9p complex; alternatively, the action of this complex may be blocked by the addition to a subset of proteins of a single α-1,2-linked mannose by a putative α-1,2-mannosyltransferase, termed M 2 MT-I by Lewis and Ballou (1991).…”

Section: Discussionmentioning

confidence: 99%

“…Ballou and co‐workers argued that Mnn9p was not part of an elongating α‐1,6‐mannosyltransferase as they could still detect α‐1,6‐transferase activity in lysates from mnn9 strains. This led them to propose that the defect was due to substrate proteins skipping the α‐1,6‐mannosyltransferase‐containing compartment (Tsai et al ., 1984; Gopal and Ballou, 1987; Lewis and Ballou, 1991). In the light of current knowledge of the secretory pathway, and the results described in this paper, it seems more likely that Mnn9p is part of two enzyme complexes directly responsible for synthesizing the backbone of the outer chain of yeast N‐linked glycans.…”

Section: Discussionmentioning

confidence: 99%

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Multi-protein complexes in the cis Golgi of Saccharomyces cerevisiae with alpha -1,6-mannosyltransferase activity

1998

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Anp1p, Van1p and Mnn9p constitute a family of membrane proteins required for proper Golgi function in Saccharomyces cerevisiae. We demonstrate that these proteins colocalize within the cis Golgi, and that they are physically associated in two distinct complexes, both of which contain Mnn9p. Furthermore, we identify two new proteins in the Anp1p-Mnn9p-containing complex which have homology to known glycosyltransferases. Both protein complexes have α-1,6-mannosyltransferase activity, forming a series of poly-mannose structures. These reaction products also contain some α-1,2-linked mannose residues. Our data suggest that these two multi-protein complexes are responsible for the synthesis and initial branching of the long α-1,6-linked backbone of the hypermannose structure attached to many yeast glycoproteins.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Multi-protein complexes in the cis Golgi of Saccharomyces cerevisiae with alpha -1,6-mannosyltransferase activity

1998

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OCH1 encodes a novel membrane bound mannosyltransferase: outer chain elongation of asparagine-linked oligosaccharides.

et al. 1992

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The Saccharomyces cerevisiae och1 mutant shows a deficiency in the mannose outer chain elongation at the non‐permissive temperature. We have cloned the OCH1 gene by complementation of temperature sensitive (ts) phenotype for growth. The integrant of OCH1 gene in the yeast chromosome can complement the ts phenotype and shows the same mapping position as that of the och1 mutation, indicating that the cloned gene is the true gene for mutation. The OCH1 gene disruptant is not lethal but ts for cell growth, and lacks mannose outer chains. The OCH1 gene sequence predicts a 55 kDa protein consisting of 480 amino acids. It contains four potential asparagine‐linked (N‐linked) glycosylation sites and a single transmembrane region near the N‐terminus. In vitro translation/translocation analysis revealed that the large C‐terminal region of the OCH1 protein is located at the lumenal side of microsomal membranes with some sugar modification, indicating a type II membrane topology. The OCH1 protein was detected in yeast membrane fractions as four forms of 58–66 kDa, which correspond to the size of a glycoprotein containing four N‐linked sugar chains the length of which is almost the same or slightly larger than the inner core (Man8GlcNAc2) formed in the endoplasmic reticulum (ER). Finally, the OCH1 gene was found to encode a novel mannosyltransferase which specifically transfers [14C]mannose to the unique acceptor, the core‐like oligosaccharide of cell wall mannan accumulated in the och1 disruptant.

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The functioning of the yeast Golgi apparatus requires an ER protein encoded by ANP1, a member of a new family of genes affecting the secretory pathway.

Chapman

Munro

1994

The EMBO Journal

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Mnt1p is an alpha 1.2‐mannosyltransferase which resides in an early compartment of the Saccharomyces cerevisiae Golgi apparatus. We have shown that the signal‐anchor region is sufficient, and the transmembrane domain necessary, for its normal Golgi localization. This is similar to the transmembrane domain‐mediated retention of mammalian glycosyltransferases, and distinct from the tail‐mediated recycling retention of certain mammalian and yeast trans‐Golgi proteins. To examine the mechanism involved in transmembrane domain‐mediated retention, we have isolated six classes of mutants which fail to retain Mnt1p‐reporter fusions in the early Golgi. These mutants all show additional phenotypes which are consistent with alterations in Golgi function. We have called the mutant classes ‘gem’, for Golgi enzyme maintenance. GEM3 is identical to the previously cloned gene ANP1, and homologous to VAN1 and MNN9. Together, these define a new class of proteins involved in the organization and functioning of the secretory pathway. Interestingly, Anp1p is localized to the endoplasmic reticulum (ER), implying that some function of the ER is required to maintain a functional Golgi apparatus.

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Separation and characterization of two alpha 1,2-mannosyltransferase activities from Saccharomyces cerevisiae

Cited by 25 publications

References 32 publications

Multi-protein complexes in the cis Golgi of Saccharomyces cerevisiae with alpha -1,6-mannosyltransferase activity

Multi-protein complexes in the cis Golgi of Saccharomyces cerevisiae with alpha -1,6-mannosyltransferase activity

OCH1 encodes a novel membrane bound mannosyltransferase: outer chain elongation of asparagine-linked oligosaccharides.

The functioning of the yeast Golgi apparatus requires an ER protein encoded by ANP1, a member of a new family of genes affecting the secretory pathway.

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