Most of the rhamnogalacturonan-I from cultured Arabidopsis cell walls is covalently linked to arabinogalactan-protein

• Published in: Carbohydrate polymers Vol. 301; no. Pt B; p. 120340
• Main Authors: Tan, Li, Zhang, Liang, Black, Ian, Glushka, John, Urbanowicz, Breeanna, Heiss, Christian, Azadi, Parastoo
• Format: Journal Article
• Language: English
• Published: United Kingdom Elsevier Ltd 01.02.2023; Elsevier
• Subjects: AGPs; Arabidopsis; arabinogalactan proteins; chemical bonding; Covalent linkage; molecular weight; NMR; nuclear magnetic resonance spectroscopy; polysaccharides; RG-I; RG-I size; RG-I-AGPs; xylose; RG-I size; NMR; Covalent linkage; RG-I-AGPs; RG-I; AGPs
• ISSN: 0144-8617; 1879-1344; 1879-1344
• DOI: 10.1016/j.carbpol.2022.120340

To characterize a purified rhamnogalacturonan-I (RG-I) containing both RG-I and arabinogalactan-protein (AGP) types of glycosyl residues, an AGP-specific β-1,3-galactanase that can cleave the AG backbone and release the AG sidechain was applied to this material. Carbohydrate analysis and NMR spectroscopy verified that the galactanase-released carbohydrate consists of RG-I covalently attached to the AG sidechain, proving a covalent linkage between RG-I and AGP. Size exclusion chromatography-multiangle light scattering-refractive index detection revealed that the galactanase-released RG-I has an average molecular weight of 41.6 kDa, which, together with the percentage of pectic sugars suggests an RG-I-AGP comprising one AGP covalently linked to two RG-I glycans. Carbohydrate analysis and NMR results of the RG-I-AGP, the galactanase-released glycans, and the RG lyase-released glycans demonstrated that the attached RG-I glycans are decorated with α-1,5-arabinan, β-1,4-galactan, xylose, and 4-O-Me-xylose sidechains. Our measurement suggests that the covalently linked RG-I-AGP is the major component of the traditionally prepared RG-I. [Display omitted] •RG-I is covalently linked to AGP.•The RG-I-AGPs are the major component of the EPG-released RG-I.•The RG-I glycans in the RG-I-AGPs are highly branched with different sidechains.•One AGP crosslinks two RG-I molecules.