Unique Asn-linked oligosaccharides of the human pathogen Entamoeba histolytica.
N-Glycans of Entamoeba histolytica, the protist that causes amebic dysentery and liver abscess, are of great interest for multiple reasons. E. histolytica makes an unusual truncated N-glycan precursor (Man(5)GlcNAc(2)), has few nucleotide sugar transporters, and has a surface that is capped by the lectin concanavalin A. Here, biochemical and mass spectrometric methods were used to examine N-glycan biosynthesis and the final N-glycans of E. histolytica with the following conclusions. Unprocessed Man(5)GlcNAc(2), which is the most abundant E. histolytica N-glycan, is aggregated into caps on the surface of E. histolytica by the N-glycan-specific, anti-retroviral lectin cyanovirin-N. Glc(1)Man(5)GlcNAc(2), which is made by a UDP-Glc: glycoprotein glucosyltransferase that is part of a conserved N-glycan-dependent endoplasmic reticulum quality control system for protein folding, is also present in mature N-glycans. A swainsonine-sensitive alpha-mannosidase trims some N-glycans to biantennary Man(3)GlcNAc(2). Complex N-glycans of E. histolytica are made by the addition of alpha1,2-linked Gal to both arms of small oligomannose glycans, and Gal residues are capped by one or more Glc. In summary, E. histolytica N-glycans include unprocessed Man(5)GlcNAc(2), which is a target for cyanovirin-N, as well as unique, complex N-glycans containing Gal and Glc.
Magnelli
Paula
P
Department of Molecular and Cell Biology, Department of Biochemistry, Boston University Medical Center, Boston, MA 02118-2526, USA.
Cipollo
John F
JF
Ratner
Daniel M
DM
Cui
Jike
J
Kelleher
Daniel
D
Gilmore
Reid
R
Costello
Catherine E
CE
Robbins
Phillips W
PW
Samuelson
John
J
D000818:Animals; D001216:Asparagine / Q000737:chemistry*; D003208:Concanavalin A / Q000737:chemistry; D004721:Endoplasmic Reticulum / Q000378:metabolism; D004748:Entamoeba histolytica / Q000378:metabolism*; D005786:Gene Expression Regulation; D006031:Glycosylation; D037102:Lectins / Q000737:chemistry; D013058:Mass Spectrometry / Q000379:methods; D008956:Models, Chemical; D008968:Molecular Conformation; D009844:Oligosaccharides / Q000737:chemistry*; D011134:Polysaccharides / Q000737:chemistry*; D017510:Protein Folding; D043323:alpha-Mannosidase / Q000737:chemistry
D037102:Lectins; D009844:Oligosaccharides; D011134:Polysaccharides; D003208:Concanavalin A; D001216:Asparagine; D043323:alpha-Mannosidase