title: Characterization of the arabinogalactan protein 31 (AGP31) of Arabidopsis thaliana: new advances on the Hyp-O-glycosylation of the Pro-rich domain.
abstract: Proteins are important actors in plant cell walls because they contribute to their architecture and their dynamics. Among them, hydroxyproline (Hyp)-rich glycoproteins constitute a complex family of O-glycoproteins with various structures and functions. In this study, we characterized an atypical Hyp-rich glycoprotein, AGP31 (arabinogalactan protein 31), which displays a multidomain organization unique in Arabidopsis thaliana, consisting of a short arabinogalactan protein (AGP) motif, a His stretch, a Pro-rich domain, and a C-terminal PAC (PRP-AGP containing Cys) domain. The use of various mass spectrometry strategies was innovative and powerful: it permitted us to locate Hyp residues, to demonstrate the presence of carbohydrates, and to refine their distribution over the Pro-rich domain. Most Hyp were isolated within repeated motifs such as KAOV, KSOV, K(PO/OP)T, K(PO/OP)V, T(PO/OP)V, and Y(PO/OP)T. A few extensin-like motifs with contiguous Hyp (SOOA and SOOT) were also found. The Pro-rich domain was shown to carry Gal residues on isolated Hyp but also Ara residues. The existence of new type Hyp-O-Gal/Ara-rich motifs not recognized by the β-glucosyl Yariv reagent but interacting with the peanut agglutinin lectin was proposed. In addition, the N-terminal short AGP motif was assumed to be substituted by arabinogalactans. Altogether, AGP31 was found to be highly heterogeneous in cell walls because arabinogalactans could be absent, Hyp-O-Gal/Ara-rich motifs of different sizes were observed, and truncated forms missing the C-terminal PAC domain were found, suggesting degradation in muro and/or partial glycosylation prior to secretion.
authors.affiliation: Université de Toulouse, UPS, UMR 5546, Laboratoire de Recherche en Sciences Végétales, BP 42617, Castanet-Tolosan, France.
authors.forename: May
authors.initials: M
authors.lastname: Hijazi
authors.forename: Jessica
authors.initials: J
authors.lastname: Durand
authors.forename: Carole
authors.initials: C
authors.lastname: Pichereaux
authors.forename: Frédéric
authors.initials: F
authors.lastname: Pont
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Jamet
authors.forename: Cécile
authors.initials: C
authors.lastname: Albenne
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006031:Glycosylation; D006909:Hydroxyproline / Q000378:metabolism*; D008969:Molecular Sequence Data; D009088:Mucoproteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary
chemical_list: C525660:AGP31 protein, Arabidopsis; D029681:Arabidopsis Proteins; D009088:Mucoproteins; D006909:Hydroxyproline