Fig. 1

The isolation and glycosyl sequence of rhamnogalacturonan-II. a Schematic representation of the extraction of non-proteinaceous pectic domains including homogalacturonan (HG), rhamnogalacturonan-I (RG-I), and rhamnogalacturonan-II (RG-II) from alcohol insoluble residue (AIR). Covalently linked multi-domain pectin molecules can be released by oxalate extraction if necessary (duckweed preparation). AIR or isolated multi-domain pectin molecules are then treated with endopolygalacturonase (EPG) to hydrolyze the HG backbone to separate the pectic domains. Purple arrowheads represent sites of EPG cleavage on the HG backbone. b The glycosyl sequence of the rhamnogalacturonan-II (RG-II) monomer. The apiosyl residue involved in the formation of the borate diester cross-linked dimer is shown. Also shown are the sites of structural diversity in RG-II glycoforms isolated from different plants with or without Araf and Rha extensions of side chain B and l-Fuc instead of l-Gal in side chain A. The RG-II structure depicted, which includes all of the known non-carbohydrate substituents, has a nominal molecular mass of 5094 Da. c The RG-II-relevant symbols from the symbol nomenclature for glycans (www.ncbi.nlm.nih.gov/glycans/snfg.html) with minor modifications so they are accessible to people with color blindness