Fasciclin-like arabinogalactan protein from Crataegi fructus

Arabinogalactan protein (AGP) was isolated from the fruits of Crataegus monogyna and C. laevigata (Rosaceae) with 3.9 % polypeptides and a carbohydrate moiety composed of Gal (57 %), Ara (35 %), Rha (1 %), and GluA (3 %). Linkage analysis, enzymatic digestion with exo-β-(1,3)-galactanase and NMR studies indicate the presence of a highly branched 1,3,6-β-D-galactose backbone with 1,6-galactan side chains, modified by the presence of α-1,5- and 1,3-linked arabinose residues. The molecular weight was determined by size exclusion chromatography with 100.6 kDa and molecular dispersity Đ of 1.71 was calculated. Data indicate the presence of a high molecular and heterodispers AGP. PNGase F treatment generated proteins of about 30 kDa, indicating that most of the carbohydrate chains are linked via asparagine and GlcNac of oligomannose or hybrid N-glycans. Mass spectrometric analysis of the tryptic digest assigned peptides of fasciclin-like arabinogalactans, which represent a subclass of AGP, responsible for cell-cell adhesion, cell sorting and embryogenesis.