Arabinogalactan proteins from stigmas of Nicotiana alata

Abstract

Stigmas of Nicotiana alata, an ornamental tobacco, contain arabinogalactan proteins (AGPS) as major components (ca 65% of the buffer-soluble high Mr carbohydrate. Glycosyl linkage analyses are compatible with a model of an arabinogalactan with a 3-linked galactan backbone substituted at C(0)6 with chains of 6-linked galactopyranosyl residues terminating in arabinofuranosyl and galactopyranosyl residues. The stigma AGPs have a low content of uronic acids (0.5-1.0% glucuronic acid). As isolated, they contain only a small amount of protein that is rich in hydroxyproline, serine, alanine, threonine, glycine, glutamate/glutamine and aspartate/asparigine. They migrate as single components with low..