title: Arabinosylation Plays a Crucial Role in Extensin Cross-linking In Vitro.
abstract: Extensins (EXTs) are hydroxyproline-rich glycoproteins (HRGPs) that are structural components of the plant primary cell wall. They are basic proteins and are highly glycosylated with carbohydrate accounting for >50% of their dry weight. Carbohydrate occurs as monogalactosyl serine and arabinosyl hydroxyproline, with arabinosides ranging in size from ~1 to 4 or 5 residues. Proposed functions of EXT arabinosylation include stabilizing the polyproline II helix structure and facilitating EXT cross-linking. Here, the involvement of arabinosylation in EXT cross-linking was investigated by assaying the initial cross-linking rate and degree of cross-linking of partially or fully de-arabinosylated EXTs using an in vitro cross-linking assay followed by gel permeation chromatography. Our results indicate that EXT arabinosylation is required for EXT cross-linking in vitro and the fourth arabinosyl residue in the tetraarabinoside chain, which is uniquely α-linked, may determine the initial cross-linking rate. Our results also confirm the conserved structure of the oligoarabinosides across species, indicating an evolutionary significance for EXT arabinosylation.
authors.affiliation: Department of Chemistry and Biochemistry, Ohio University, Athens, OH, USA.
authors.forename: Yuning
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Department of Chemistry and Biochemistry, Ohio University, Athens, OH, USA.
authors.forename: Wen
authors.initials: W
authors.lastname: Dong
authors.affiliation: Complex Carbohydrate Research Center, University of Georgia, Athens, GA, USA.
authors.forename: Li
authors.initials: L
authors.lastname: Tan
authors.affiliation: Department of Chemistry and Biochemistry, Ohio University, Athens, OH, USA.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Held
authors.affiliation: Department of Chemistry and Biochemistry, Ohio University, Athens, OH, USA.
authors.forename: Marcia J
authors.initials: MJ
authors.lastname: Kieliszewski
keywords: HRGP; RSH; arabinosylation; extensin; in vitro cross-linking; peroxidase; tomato P1