High impact information on MNS1

• Disruption of the MNS1 gene resulted in undetectable specific alpha-mannosidase activity but no apparent effect on growth [1].
• Interaction of the endoplasmic reticulum alpha 1,2-mannosidase Mns1p with Rer1p using the split-ubiquitin system [2].
• The alpha1,2-mannosidase Mns1p involved in the N-glycosidic pathway in Saccharomyces cerevisiae is a type II membrane protein of the endoplasmic reticulum [2].
• The importance of mannose removal for subsequent outer chain synthesis was examined in strains of S. cerevisiae disrupted in the MNS1 gene encoding a specific alpha 1,2-mannosidase responsible for Man8GlcNAc2 synthesis [Camirand, Heysen, Grondin and Herscovics (1991) J. Biol. Chem. 266, 15120-15127] [3].
• H.p.l.c. of the included oligosaccharides showed that a Man9GlcNAc, rather than a Man8GlcNAc, intermediate was formed in mns1 cells [3].

Biological context of MNS1

• Invertase immunoprecipitated from [35S]methionine-labelled mns1 cells was highly glycosylated, but migrated slightly faster than that from control cells on denaturing PAGE, indicating a small difference in glycosylation [3].
• Mns1p is a 68 kDa type II integral membrane glycoprotein with a very short amino terminal cytoplasmic tail of only two amino acids and a large carboxy-terminal catalytic region that is homologous to class 1 alpha 1,2-mannosidases from mammalian and other species [4].

Associations of MNS1 with chemical compounds

• As Mns1p contains none of the known endoplasmic reticulum retrieval motifs (HDEL, KK or RR), these results suggest that Mns1p is localized in the endoplasmic reticulum by a different retentin mechanism [4].

Analytical, diagnostic and therapeutic context of MNS1

• Co-expression of NubG-Mns1p and Rer1p-Cub-protein A-lexA-VP16 in L40 yeast cells resulted in cleavage of the reporter molecule, protein A-lexA-VP16, detected by western blot analysis and by expression of beta-galactosidase activity [2].
• Both MNS1 transcripts of 1.85 kb and 1.7 kb were not observed in Northern blots of mns1 cells (i.e. cells containing the disrupted gene) [3].
• We have used immunofluorescence and immunoelectron microscopy to demonstrate that Mns1p is localized in the endoplasmic reticulum in Saccharomyces cerevisiae [4].

References