Identification of the MNN2 and MNN5Mannosyltransferases Required for Forming and Extending the Mannose Branches of the Outer Chain Mannans of Saccharomyces cerevisiae

Rayner, Julian C.; Munro, Sean

doi:10.1074/jbc.273.41.26836

Cited by 112 publications

(111 citation statements)

References 57 publications

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“…Mannan side branching and mannose phosphate addition: Branching of the a1,6 mannan backbone is initiated by the Mnn2 a1,2-Man-T, and Mnn5 adds a second a1,2-Man (Rayner and Munro 1998). Mnn2 and Mnn5 make up one of two Mnn1 subfamilies .…”

Section: N-glycosylationmentioning

confidence: 99%

Architecture and Biosynthesis of the Saccharomyces cerevisiae Cell Wall

2012

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The wall gives a Saccharomyces cerevisiae cell its osmotic integrity; defines cell shape during budding growth, mating, sporulation, and pseudohypha formation; and presents adhesive glycoproteins to other yeast cells. The wall consists of b1,3-and b1,6-glucans, a small amount of chitin, and many different proteins that may bear N-and O-linked glycans and a glycolipid anchor. These components become cross-linked in various ways to form higher-order complexes. Wall composition and degree of cross-linking vary during growth and development and change in response to cell wall stress. This article reviews wall biogenesis in vegetative cells, covering the structure of wall components and how they are cross-linked; the biosynthesis of N-and O-linked glycans, glycosylphosphatidylinositol membrane anchors, b1,3-and b1,6-linked glucans, and chitin; the reactions that cross-link wall components; and the possible functions of enzymatic and nonenzymatic cell wall proteins. TABLE OF CONTENTS Abstract 775Introduction 777

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Section: N-glycosylationmentioning

confidence: 99%

Architecture and Biosynthesis of the Saccharomyces cerevisiae Cell Wall

2012

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“…For proteins that receive a core-type structure an as yet unidentified enzyme adds an ␣-1,2-linked mannose to the mannose added by Och1p, followed by terminal ␣-1,3-linked mannoses from Mnn1p (17,18). In contrast, on mannoproteins an ␣-1,6-linked mannose is attached to the mannose added by Och1p, and this is then extended to generate a long ␣-1,6-linked backbone which is then branched by the addition of ␣-1,2-linked and then ␣-1,3-linked mannoses (19,20). The mannan backbone is generated by two multiprotein complexes called mannan polymerase (M-Pol) I and II (21)(22)(23).…”

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confidence: 99%

The Components of the Saccharomyces cerevisiaeMannosyltransferase Complex M-Pol I Have Distinct Functions in Mannan Synthesis

Stolz

Munro

2002

Journal of Biological Chemistry

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The yeast Saccharomyces cerevisiae processes N-linked glycans in the Golgi apparatus in two different ways. Whereas most of the proteins of internal membranes receive a simple core-type structure, a long branched polymer termed mannan is attached to the glycans of many of the proteins destined for the cell wall. The first step in mannan synthesis is the initiation and extension of an ␣-1,6-linked polymannose backbone. This requires the sequential action of two enzyme complexes, mannan polymerases (M-Pol) I and II. M-Pol I contains the proteins Mnn9p and Van1p, although the stoichiometry and individual contributions to enzyme action are unclear. We report here that the two proteins are each present as a single copy in the complex. Both proteins contain a DXD motif found in the active site of many glycosyltransferases, and mutations in this motif in Mnn9p or Van1p reveal that both proteins contribute to mannose polymerization. However, the effects of these mutations on both the in vivo and in vitro activity are distinct, suggesting that the two proteins may have different roles in the complex. Finally, we show that a simple glycoprotein based on hen egg lysozyme can be used as a substrate for modification by purified M-Pol I in vitro.

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“…Curiously, the same situation is found in sequons 2 (Asn 45 -Asp-Thr), 3 (Asn 78 -Asp-Ser) and 6 (Asn 99 - 3 Numbers in bold identify the order of the sequon starting from the N terminus. 4 Numbers in parentheses refer to the position of the Asn of each sequon in the sequences of Inv1 and Suc2.…”

Section: Discussionmentioning

confidence: 99%

A Search for Hyperglycosylation Signals in Yeast Glycoproteins

Conde

Cueva

Pablo

et al. 2004

Journal of Biological Chemistry

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N-oligosaccharides of Saccharomyces cerevisiae glycoproteins are classified as core and mannan types. The former contain 13-14 mannoses whereas mannan-type structures consist of an inner core extended with an outer chain of up to 200 -300 mannoses, a process known as hyperglycosylation. The selection of substrates for hyperglycosylation poses a theoretical and practical question. To identify hyperglycosylation determinants, we have analyzed the influence of the second amino acid (Xaa) of the sequon in this process using the major exoglucanase as a model. Our results indicate that negatively charged amino acids inhibit hyperglycosylation, whereas positively charged counterparts promote it. On the basis of the tridimensional structure of Exg1, we propose that Xaa influences the orientation of the inner core making it accessible to mannan polymerase I in the appropriate position for the addition of ␣-1,6-mannoses. The presence of Glu in the Xaa of the second sequon of the native exoglucanase suggests that negative selection may drive evolution of these sites. However, a comparison of invertases secreted by S. cerevisiae and Pichia anomala suggests that hyperglycosylation signals are also subjected to positive selection.Protein glycosylation in eukaryotic cells is thought to play an essential role in many processes such as protein folding and transport, maintenance of protein and cell structure, and cell recognition and adhesion, as well as other functions. From the several types of protein glycosylation, N-glycosylation has received a great deal of attention not only because of its high frequency but also because several biochemical steps involved in this biosynthetic process are shared by yeast and humans, an indication that they have been conserved throughout evolution. These conserved steps occur in the membrane (i) or the lumen (ii and iii) of the ER 1 and belong to three groups: (i) assembly of the precursor oligosaccharide, GlnNAc 2 -Man 9 Glc 3 on a lipid carrier (dolichol-PP), (ii) transfer of the oligosaccharide to the nascent or recently synthesized protein acceptor, and (iii) trimming of the three glucoses and one mannose (for recent reviews, see Refs. 1 and 2).However, once the glycoprotein leaves the ER, biochemical modification by trimming and/or addition of new sugars varies enormously between species and even between individual proteins of the same cell. This suggests that individual proteins carry the precise information for the final carbohydrate composition. In Saccharomyces cerevisiae, some of the protein-attached oligosaccharides leaving the ER (GlcNAc 2 -Man 8 ) are poorly elongated with up to 13-14 mannoses (coretype), whereas many others are further elongated by the addition of an outer chain of up to 200 mannose residues in the Golgi apparatus (mannan-type), a process commonly known as hyperglycosylation. The outer chain consists of a backbone of ␣-1,6-mannoses with ␣-1,2 branches that are decorated with terminal ␣-1,3-mannose residues (1, 3). The biosynthesis of this complex is carried out...

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Identification of the MNN2 and MNN5Mannosyltransferases Required for Forming and Extending the Mannose Branches of the Outer Chain Mannans of Saccharomyces cerevisiae

Cited by 112 publications

References 57 publications

Architecture and Biosynthesis of the Saccharomyces cerevisiae Cell Wall

Architecture and Biosynthesis of the Saccharomyces cerevisiae Cell Wall

The Components of the Saccharomyces cerevisiaeMannosyltransferase Complex M-Pol I Have Distinct Functions in Mannan Synthesis

A Search for Hyperglycosylation Signals in Yeast Glycoproteins

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