title: Biochemical evidence for an alternate pathway in N-linked glycoprotein biosynthesis.
abstract: Asparagine-linked glycosylation is a complex protein modification conserved among all three domains of life. Herein we report the in vitro analysis of N-linked glycosylation from the methanogenic archaeon Methanococcus voltae. Using a suite of synthetic and semisynthetic substrates, we show that AglK initiates N-linked glycosylation in M. voltae through the formation of α-linked dolichyl monophosphate N-acetylglucosamine, which contrasts with the polyprenyl diphosphate intermediates that feature in both eukaryotes and bacteria. Notably, AglK has high sequence homology to dolichyl phosphate β-glucosyltransferases, including Alg5 in eukaryotes, suggesting a common evolutionary origin. The combined action of the first two enzymes, AglK and AglC, afforded an α-linked dolichyl monophosphate glycan that serves as a competent substrate for the archaeal oligosaccharyl transferase AglB. These studies provide what is to our knowledge the first biochemical evidence revealing that, despite the apparent similarity of the overall pathways, there are actually two general strategies to achieve N-linked glycoproteins across the domains of life.
authors.affiliation: Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA.
authors.forename: Angelyn
authors.initials: A
authors.lastname: Larkin
authors.forename: Michelle M
authors.initials: MM
authors.lastname: Chang
authors.forename: Garrett E
authors.initials: GE
authors.lastname: Whitworth
authors.forename: Barbara
authors.initials: B
authors.lastname: Imperiali
mesh_terms: D019843:Archaeal Proteins / Q000737:chemistry; D004926:Escherichia coli / Q000378:metabolism; D019143:Evolution, Molecular; D005786:Gene Expression Regulation; D005964:Glucosyltransferases / Q000737:chemistry; D006020:Glycopeptides / Q000737:chemistry; D006023:Glycoproteins / Q000737:chemistry*; D006031:Glycosylation; D008055:Lipids / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D017017:Methanococcus / Q000737:chemistry*; D010957:Plasmids / Q000378:metabolism; D011134:Polysaccharides / Q000737:chemistry
chemical_list: D019843:Archaeal Proteins; D006020:Glycopeptides; D006023:Glycoproteins; D008055:Lipids; D011134:Polysaccharides; D005964:Glucosyltransferases