Cg. Chen et al., MOLECULAR-CLONING OF A GENE ENCODING AN ARABINOGALACTAN PROTEIN FROM PEAR (PYRUS-COMMUNIS) CELL-SUSPENSION CULTURE, Proceedings of the National Academy of Sciences of the United Statesof America, 91(22), 1994, pp. 10305-10309
Arabinogalactan proteins (AGPs) are proteoglycans containing a high pr
oportion of carbohydrate (typically >90%) linked to a protein backbone
rich in hydroxyproline (Hyp), Ala, Ser, and Thr. They are widely dist
ributed in plants and may play a role in development. The structure of
the carbohydrate of some AGPs is known in detail but information rega
rding the protein backbone is restricted to a few peptide sequences. H
ere we report isolation and partial amino acid sequencing of the prote
in backbone of an AGP, This AGP is a member of one of four major group
s of AGPs isolated from the filtrate of pear cell suspension culture.
A cDNA encoding this protein backbone (145 amino acids) was cloned; th
e deduced protein is rich in Hyp, Ala, Ser, and Thr, which together ac
count for >75% of total residues. It has three domains, an N-terminal
secretion signal, a central hydrophilic domain containing all of the P
ro residues, and a hydrophobic C-terminal domain that is predicted to
be a transmembrane helix. Approximately 93% of the Pro residues are hy
droxylated and hence are potential sites for glycosylation.