title: Structure of N-linked oligosaccharides attached to chlorovirus PBCV-1 major capsid protein reveals unusual class of complex N-glycans.
abstract: The major capsid protein Vp54 from the prototype chlorovirus Paramecium bursaria chlorella virus 1 (PBCV-1) contains four Asn-linked glycans. The structure of the four N-linked oligosaccharides and the type of substitution at each glycosylation site was determined by chemical, spectroscopic, and spectrometric analyses. Vp54 glycosylation is unusual in many ways, including: (i) unlike most viruses, PBCV-1 encodes most, if not all, of the machinery to glycosylate its major capsid protein; (ii) the glycans are attached to the protein by a β-glucose linkage; (iii) the Asn-linked glycans are not located in a typical N-X-(T/S) consensus site; and (iv) the process probably occurs in the cytoplasm. The four glycoforms share a common core structure, and the differences are related to the nonstoichiometric presence of two monosaccharides. The most abundant glycoform consists of nine neutral monosaccharide residues, organized in a highly branched fashion. Among the most distinctive features of the glycoforms are (i) a dimethylated rhamnose as the capping residue of the main chain, (ii) a hyperbranched fucose unit, and (iii) two rhamnose residues with opposite absolute configurations. These glycoforms differ from what has been reported so far in the three domains of life. Considering that chloroviruses and other members of the family Phycodnaviridae may have a long evolutionary history, we suggest that the chlorovirus glycosylation pathway is ancient, possibly existing before the development of the endoplasmic reticulum and Golgi pathway, and involves still unexplored mechanisms.
authors.affiliation: Department of Chemical Sciences, University of Napoli Federico II, 80126 Naples, Italy.
authors.forename: Cristina
authors.initials: C
authors.lastname: De Castro
authors.forename: Antonio
authors.initials: A
authors.lastname: Molinaro
authors.forename: Francesco
authors.initials: F
authors.lastname: Piacente
authors.forename: James R
authors.initials: JR
authors.lastname: Gurnon
authors.forename: Luisa
authors.initials: L
authors.lastname: Sturiale
authors.forename: Angelo
authors.initials: A
authors.lastname: Palmigiano
authors.forename: Rosa
authors.initials: R
authors.lastname: Lanzetta
authors.forename: Michelangelo
authors.initials: M
authors.lastname: Parrilli
authors.forename: Domenico
authors.initials: D
authors.lastname: Garozzo
authors.forename: Michela G
authors.initials: MG
authors.lastname: Tonetti
authors.forename: James L
authors.initials: JL
authors.lastname: Van Etten
mesh_terms: D036022:Capsid Proteins / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D002708:Chlorella / Q000821:virology*; D011088:DNA Ligases / Q000737:chemistry* / Q000378:metabolism; D008401:Gas Chromatography-Mass Spectrometry; D009682:Magnetic Resonance Spectroscopy; D009005:Monosaccharides / Q000737:chemistry; D009844:Oligosaccharides / Q000737:chemistry* / Q000378:metabolism; D010247:Paramecium / Q000382:microbiology*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D014764:Viral Proteins / Q000737:chemistry* / Q000378:metabolism
chemical_list: D036022:Capsid Proteins; D009005:Monosaccharides; D009844:Oligosaccharides; D014764:Viral Proteins; C110456:Chlorella virus DNA ligase; D011088:DNA Ligases
keywords: cytoplasmic glycosylation; glucose/asparagine linkage; glycobiology; glycopeptide; virus-encoded glycosylation
references.citation: J Biol Chem. 1985 Dec 5;260(28):15180-5
references.pmid: 3934156
references.citation: J Virol. 2011 May;85(9):4520-9
references.pmid: 21289127
references.citation: Trends Plant Sci. 2012 Jan;17(1):1-8
references.pmid: 22100667
references.citation: Virology. 1983 Apr 15;126(1):117-25
references.pmid: 18638936
references.citation: Proc Natl Acad Sci U S A. 1993 May 1;90(9):3840-4
references.pmid: 7683409
references.citation: Science. 2004 Nov 19;306(5700):1344-50
references.pmid: 15486256
references.citation: J Biol Chem. 2013 Apr 19;288(16):11093-105
references.pmid: 23436655
references.citation: Biochim Biophys Acta. 2010 Feb;1800(2):152-9
references.pmid: 19654039
references.citation: J Virol. 2006 Aug;80(16):8114-23
references.pmid: 16873267
references.citation: J Biol Chem. 2008 Sep 19;283(38):26010-5
references.pmid: 18621734
references.citation: Virology. 1994 Sep;203(2):320-7
references.pmid: 8053156
references.citation: J Cell Biol. 1994 Mar;124(6):1071-81
references.pmid: 8132707
references.citation: Trends Microbiol. 2007 May;15(5):211-8
references.pmid: 17398101
references.citation: J Biol Chem. 1992 Apr 25;267(12):8182-5
references.pmid: 1569073
references.citation: Nat Rev Microbiol. 2007 Oct;5(10):801-12
references.pmid: 17853907
references.citation: J Virol. 2000 Aug;74(15):7079-84
references.pmid: 10888648
references.citation: PLoS Pathog. 2010 May 27;6(5):e1000919
references.pmid: 20523900
references.citation: J Biol Chem. 2003 Jun 13;278(24):21559-65
references.pmid: 12679342
references.citation: Carbohydr Res. 2013 Apr 5;370:9-12
references.pmid: 23419941
references.citation: Virology. 2001 Jul 5;285(2):332-45
references.pmid: 11437667
references.citation: Virus Res. 2006 Apr;117(1):156-84
references.pmid: 16494962
references.citation: Methods Enzymol. 2010;480:89-115
references.pmid: 20816206
references.citation: Virus Res. 2006 Apr;117(1):119-32
references.pmid: 16516998
references.citation: Scand J Infect Dis. 1998;30(5):435-40
references.pmid: 10066039
references.citation: Carbohydr Res. 2008 Sep 22;343(14):2401-5
references.pmid: 18657801
references.citation: Science. 1983 Feb 25;219(4587):994-6
references.pmid: 17817937
references.citation: J Biol Chem. 2011 Oct 7;286(40):35267-74
references.pmid: 21852240
references.citation: J Virol. 2012 Aug;86(16):8821-34
references.pmid: 22696644
references.citation: Biochim Biophys Acta. 1989 Apr 26;1002(3):333-7
references.pmid: 2653442
references.citation: Proc Natl Acad Sci U S A. 1983 Sep;80(18):5470-4
references.pmid: 16593364
references.citation: Biochemistry. 1991 Aug 6;30(31):7772-7
references.pmid: 1868054
references.citation: J Biol Chem. 2012 Jan 27;287(5):3009-18
references.pmid: 22157758
references.citation: J Virol. 2001 Dec;75(23):11720-34
references.pmid: 11689653
references.citation: Proc Natl Acad Sci U S A. 2002 Nov 12;99(23):14758-63
references.pmid: 12411581
references.citation: Annu Rev Genet. 2003;37:153-95
references.pmid: 14616059
references.citation: Virology. 1993 Apr;193(2):545-62
references.pmid: 8460475