ALG3 / YBL082C Overview

Standard Name
ALG3 1
Systematic Name
RHK1 3
Feature Type
ORF , Verified
Dolichol-P-Man dependent alpha(1-3) mannosyltransferase; involved in synthesis of dolichol-linked oligosaccharide donor for N-linked glycosylation of proteins; G353A missense mutation in human ortholog ALG3 implicated in carbohydrate deficient glycoprotein syndrome type IV, which is characterized by microcephaly, severe epilepsy, minimal psychomotor development, partial deficiency of sialic acids in serum glycoproteins; wild-type human ALG3 can complement yeast alg3 mutant 2 3 4 5
Name Description
Asparagine Linked Glycosylation 1
Comparative Info
Sequence Details


The S. cerevisiae Reference Genome sequence is derived from laboratory strain S288C. Download DNA or protein sequence, view genomic context and coordinates. Click "Sequence Details" to view all sequence information for this locus, including that for other strains.

Protein Details


Basic sequence-derived (length, molecular weight, isoelectric point) and experimentally-determined (median abundance, median absolute deviation) protein information. Click "Protein Details" for further information about the protein such as half-life, abundance, domains, domains shared with other proteins, protein sequence retrieval for various strains, physico-chemical properties, protein modification sites, and external identifiers for the protein.

Length (a.a.)
Mol. Weight (Da)
Isoelectric Point
Median Abundance (molecules/cell)
1472 +/- 390
Half-life (hr)


Curated mutant alleles for the specified gene, listed alphabetically. Click on the allele name to open the allele page. Click "SGD search" to view all alleles in search results. Click "YeastMine" to view all alleles in YeastMine.

View all ALG3 alleles in SGD search | YeastMine

Gene Ontology Details

Gene Ontology

GO Annotations consist of four mandatory components: a gene product, a term from one of the three Gene Ontology (GO) controlled vocabularies (Molecular Function, Biological Process, and Cellular Component), a reference, and an evidence code. SGD has manually curated and high-throughput GO Annotations, both derived from the literature, as well as computational, or predicted, annotations. Click "Gene Ontology Details" to view all GO information and evidence for this locus as well as biological processes it shares with other genes.

Alpha-1,3-mannosyltransferase that transfers a mannose residue to an oligosaccharide; involved in protein glycosylation and the assembly of oligosaccharide-lipid intermediates; localizes to the endoplasmic reticulum

View computational annotations

Biological Process

Manually Curated

Cellular Component

Manually Curated


Phenotype Details


Phenotype annotations for a gene are curated single mutant phenotypes that require an observable (e.g., "cell shape"), a qualifier (e.g., "abnormal"), a mutant type (e.g., null), strain background, and a reference. In addition, annotations are classified as classical genetics or high-throughput (e.g., large scale survey, systematic mutation set). Whenever possible, allele information and additional details are provided. Click "Phenotype Details" to view all phenotype annotations and evidence for this locus as well as phenotypes it shares with other genes.

Non-essential gene; null mutant is sensitive to reducing agents such as mercaptoethanol and DTT; null mutant has increased replicative and chronological lifespans and is resistant to killer toxin HM-1; in large-scale studies, null mutant shows reductions in competitive fitness, desiccation resistance, vegetative growth, and respiratory growth
Disease Details


Disease Annotations consist of three mandatory components: a gene product, a term from the Disease Ontology (DO) controlled vocabulary and an evidence code. SGD provides manually curated DO Annotations derived from the literature. Click "Disease Details" to view all Disease information and evidence for this locus as well as diseases it shares with other genes.

Yeast ALG3 is homologous to human ALG3, and has been used to study congenital disorder of glycosylation
Interaction Details


Interaction annotations are curated by BioGRID and include physical or genetic interactions observed between at least two genes. An interaction annotation is composed of the interaction type, name of the interactor, assay type (e.g., Two-Hybrid), annotation type (e.g., manual or high-throughput), and a reference, as well as other experimental details. Click "Interaction Details" to view all interaction annotations and evidence for this locus, including an interaction visualization.

310 total interactions for 187 unique genes

Physical Interactions

  • Affinity Capture-MS: 5
  • Affinity Capture-RNA: 2
  • PCA: 1
  • Two-hybrid: 1

Genetic Interactions

  • Dosage Rescue: 2
  • Negative Genetic: 208
  • Phenotypic Enhancement: 8
  • Phenotypic Suppression: 36
  • Positive Genetic: 39
  • Synthetic Growth Defect: 5
  • Synthetic Lethality: 3
Regulation Details


The number of putative Regulators (genes that regulate it) and Targets (genes it regulates) for the given locus, based on experimental evidence. This evidence includes data generated through high-throughput techniques. Click "Regulation Details" to view all regulation annotations, shared GO enrichment among regulation Targets, and a regulator/target diagram for the locus.

ALG3 encodes an alpha-1,3-mannosyltransferase involved in the first step of N-linked glycosylation of proteins in the endoplasmic reticulum (ER) - the assembly of the lipid-linked oligosaccharide (LLO), which then serves as a donor in the second step - the transfer of the oligosaccharide to asparagine residues of nascent polypeptides. The lipid component that anchors the LLO in the ER membrane is dolichol (Dol), a polyisoprenoid molecule composed in yeast of 15-16 isoprene units. The LLO assembly involves sequential additions of two N-acetylglucosamine (GlcNAc), nine mannose (Man), and three glucose (Glc) residues. Alg3p catalyzes the addition of a Man residue to LLO after the earlier steps catalyzed by UDP-GlcNAc transferases Alg7p and Alg13p-Alg14p, an alpha-1,3- and alpha-1,6-mannosyltransferase Alg2p, and an alpha-1,2-mannosyltransferase Alg11p that take place on the cytoplasmic side of the ER membrane. After the product, Dol-PP-GlcNAc2-Man5, is flipped to the ER lumen by an unknown flippase, the oligosaccharide chain is elongated by four more Man residues, in reactions catalyzed by mannosyltransferases Alg3p, Alg12p and Alg9p, and three Glc residues, catalyzed by glucosyltransferases Alg6p, Alg8p and Alg10p. The final product delivers the 14 glycan molecule to the hetero-oligomeric oligosaccharyltransferase (Ost) complex (Ost1p, Ost2p, Ost3p, Ost4p, Ost5p, Ost6p, Stt3p, Swp1p, and Wbp1p), which transfers the entire oligosaccharide chain to asparagine side chains in polypeptides. The entire process that leads to the assembly of the LLO must be strictly ordered and the order appears to be ensured by high substrate specificities of all the participating ALG enzymes. The regulation of the activities appears to occur at the level of substrate availability, and the rate-limiting factor may be the amount of Dol-P on the cytoplasmic side of the ER membrane, which seems to be primarily affected by recycling of Dol-PP released by the Ost complex. The initial steps of protein N-glycosylation are remarkably conserved in evolution and most of the yeast genes involved in this process have their known homologs in humans, many of which are implicated in severe disorders such as the CDG syndrome (congenital disorders of glycosylation) as well as congenital muscular dystrophies.
Expression Details


Expression data are derived from records contained in the Gene Expression Omnibus (GEO), and are first log2 transformed and normalized. Referenced datasets may contain one or more condition(s), and as a result there may be a greater number of conditions than datasets represented in a single clickable histogram bar. The histogram division at 0.0 separates the down-regulated (green) conditions and datasets from those that are up-regulated (red). Click "Expression Details" to view all expression annotations and details for this locus, including a visualization of genes that share a similar expression pattern.

Summary Paragraph

A summary of the locus, written by SGD Biocurators following a thorough review of the literature. Links to gene names and curated GO terms are included within the Summary Paragraphs.

Last Updated: 2005-07-01

Literature Details


All manually curated literature for the specified gene, organized into topics according to their relevance to the gene (Primary Literature, Additional Literature, or Review). Click "Literature Details" to view all literature information for this locus, including shared literature between genes.