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2.4.1.260: dolichyl-P-Man:Man7GlcNAc2-PP-dolichol alpha-1,6-mannosyltransferase

This is an abbreviated version!
For detailed information about dolichyl-P-Man:Man7GlcNAc2-PP-dolichol alpha-1,6-mannosyltransferase, go to the full flat file.

Word Map on EC 2.4.1.260

Reaction

dolichyl beta-D-mannosyl phosphate
+
alpha-D-Man-(1->2)-alpha-D-Man-(1->2)-alpha-D-Man-(1->3)-[alpha-D-Man-(1->2)-alpha-D-Man-(1->3)-alpha-D-Man-(1->6)]-beta-D-Man-beta-(1->4)-beta-D-GlcNAc-(1->4)-alpha-D-GlcNAc-diphosphodolichol
=
alpha-D-Man-alpha-(1->2)-alpha-D-Man-(1->2)-alpha-D-Man-(1->3)-[alpha-D-Man-(1->2)-alpha-D-Man-(1->3)-[alpha-D-Man-(1->6)]-alpha-D-Man-(1->6)]-beta-D-Man-(1->4)-beta-D-GlcNAc-(1->4)-alpha-D-GlcNAc-diphosphodolichol
 +
dolichyl phosphate

Synonyms

ALG12, ALG12 alpha1,6mannosyltransferase, ALG12 mannosyltransferase, alpha1-6-mannosyltransferase, Dol-P-Man:Man7GlcNAc2-PP-Dol-alpha1-6-mannosyltransferase, dolichyl-P-Man:Man7GlcNAc2-PP-dolichyl alpha6-mannosyltransferase, dolichyl-P-mannose:Man7GlcNAc2-PP-dolichyl mannosyltransferase, EBS4, EC 2.4.1.130, TbALG12

ECTree

     2 Transferases
         2.4 Glycosyltransferases
             2.4.1 Hexosyltransferases
                2.4.1.260 dolichyl-P-Man:Man7GlcNAc2-PP-dolichol alpha-1,6-mannosyltransferase

Engineering

Engineering on EC 2.4.1.260 - dolichyl-P-Man:Man7GlcNAc2-PP-dolichol alpha-1,6-mannosyltransferase

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PROTEIN VARIANTS
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
E38K
the wild-type EBS4 gene but not the mutated EBS4 plasmid carrying the E38K mutation (ebs4-3) is able to complement the yeast DELTAalg12 mutation
R100W
residue R100 is located near the end of the largest luminal loop between the first two predicted transmembrane segments and is absolutely conserved in all known ALG9 enzymes. Mutation suppresses a dwarf mutant, bri1-9, the phenotypes of which are caused by endoplasmic reticulum retention and endoplasmic reticulum-associated degradation of a brassinosteroid receptor, BRASSINOSTEROID-INSENSITIVE 1, BR1. The mutation prevents the Glc3Man9GlcNAc2 assembly and inhibits the endoplasmic reticulum-associated degradation of bri1-9. Overexpression of EBS4 in the R100W bri1-9 mutant, which encodes the Arabidopsis ortholog of the yeast ALG12 catalyzing the ER luminal alpha1,6 Man addition, adds an alpha1,6 Man to the truncated N-glycan precursor accumulated in R100W bri1-9, promotes the bri1-9 endoplasmic reticulum-associated degradation, and neutralizes the R100W suppressor phenotype
T70I
mutation leads to attenuated calcium response to the bacterial flagellin flg22 peptide and several other elicitors. Mutant protein is correctly targeted to the plasma membrane, and several of the receptors expressed in the T70I background are underglycosylated
F142V
the F142V replacement in hALG12p is the cause of inefficient addition of the eighth mannose residue onto Man7GlcNAc2-PP-dolichol during glycoprotein biosynthesis in a patient with type I congenital disorders of glycosylation. The patient is homozygous for the point mutation that causes an amino acid substitution in a conserved region of dolichyl-P-Man:Man7GlcNAc2-PP-dolichyl alpha6-mannosyltransferase. Skin biopsy fibroblasts from a CDG I patient have a reduced capacity to add the eighth mannose residue onto the lipid-linked oligosaccharide precursor. The fibroblasts of the patient are capable of the direct transfer of Man7GlcNAc2 from dolichol onto protein and that this N-linked structure can be glucosylated by UDP-glucose:glycoprotein glucosyltransferase in the endoplasmic reticulum
R146Q
congenital disorder of glycosylation type lg is identified in a child presenting with psychomotor retardation, hypotonia, growth retardation, dysmorphic features and anorexia. In the patient’s fibroblasts, the biosynthetic intermediate GlcNAc2Man7 oligosaccharide is detected both on the lipid carrier dolichyl pyrophosphate and on newly synthesized glycoproteins, pointing to a defect in the dolichyl pyrophosphate–GlcNAc2Man7-dependent ALG12 alpha1,6 mannosyltransferase. Analysis of the ALG12 cDNA in the CDG patient revealed compound heterozygosity for two point mutations that result in the amino acid substitutions T67M and R146Q, respectively. The impact of these mutations on ALG12 protein function is investigated in the Saccharomyces cerevisiae alg12 glycosylation mutant by showing that the yeast ALG12 gene bearing the homologous mutations T61M and R161Q and the human mutant ALG12 cDNA alleles fail to normalize the growth defect phenotype of the alg12 yeast model, whereas expression of the normal ALG12 cDNA complements the yeast mutation. The ALG12 mannosyltransferase defect defines a type of congenital disorder of glycosylation, designated CDG-Ig
T67M
congenital disorder of glycosylation type lg is identified in a child presenting with psychomotor retardation, hypotonia, growth retardation, dysmorphic features and anorexia. In the patient’s fibroblasts, the biosynthetic intermediate GlcNAc2Man7 oligosaccharide is detected both on the lipid carrier dolichyl pyrophosphate and on newly synthesized glycoproteins, pointing to a defect in the dolichyl pyrophosphate–GlcNAc2Man7-dependent ALG12 alpha1,6 mannosyltransferase. Analysis of the ALG12 cDNA in the CDG patient revealed compound heterozygosity for two point mutations that result in the amino acid substitutions T67M and R146Q, respectively. The impact of these mutations on ALG12 protein function is investigated in the Saccharomyces cerevisiae alg12 glycosylation mutant by showing that the yeast ALG12 gene bearing the homologous mutations T61M and R161Q and the human mutant ALG12 cDNA alleles fail to normalize the growth defect phenotype of the alg12 yeast model, whereas expression of the normal ALG12 cDNA complements the yeast mutation. The ALG12 mannosyltransferase defect defines a type of congenital disorder of glycosylation, designated CDG-Ig