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Molecular cloning of a gene encoding an arabinogalactan-protein from pear (Pyrus communis) cell suspension culture
- Chen, C.G., Pu, Z.Y., Moritz, R.L., Simpson, R.J., Bacic, A., Clarke, A.E., Mau, S.L.
- Proceedings of the National Academy of Sciences of the United States of America 1994 v.91 no.22 pp. 10305-10309
- Pyrus communis, complementary DNA, structural genes, glycoproteins, apoproteins, plant proteins, nucleotide sequences, amino acid sequences, cell suspension culture, galactans, arabinose
- Arabinogalactan-proteins (AGPs) are proteoglycans containing a high proportion of carbohydrate (typically > 90%) linked to a protein backbone rich in hydroxyproline (Hyp), Ala, Ser, and Thr. They are widely distributed in plants and may play a role in development. The structure of the carbohydrate of some AGPs is known in detail but information regarding the protein backbone is restricted to a few peptide sequences. Here we report isolation and partial amino acid sequencing of the protein backbone of an AGP. This AGP is a member of one of four major groups of AGPs isolated from the filtrate of pear cell suspension culture. A cDNA encoding this protein backbone (145 amino acids) was cloned; the deduced protein is rich in Hyp, Ala, Ser, and Thr, which together account for > 75% of total residues. It has three domains, an N-terminal secretion signal, a central hydrophilic domain containing all of the Pro residues, and a hydrophobic C-terminal domain that is predicted to be a transmembrane helix. Approximately 93% of the Pro residues are hydroxylated and hence are potential sites for glycosylation.