J. Svetek et al., Presence of a glycosylphosphatidylinositol lipid anchor on rose arabinogalactan proteins, J BIOL CHEM, 274(21), 1999, pp. 14724-14733
Arabinogalactan proteins constitute a class of plant cell surface proteogly
cans with widespread occurrence and suggested functions in various aspects
of plant growth and development, including cell proliferation, expansion, m
arking, and death. Previous investigations of subcellular fractions from su
spension-cultured cells of "Paul's Scarlet" rose (Rosa sp.) have revealed e
xtensive structural similarity between some soluble arabinogalactan protein
s from the cell wall space and some plasma membrane-associated arabinogalac
tan proteins, thus inspiring the present investigation of the mechanism thr
ough which these inherently water-soluble molecules are held on the plasma
membrane. Several lines of evidence gained through a combination of methods
including reversed-phase chromatography, treatment with phosphatidylinosit
ol-specific phospholipase C, and chemical structural analysis now show that
some rose arabinogalactan proteins carry a ceramide class glycosylphosphat
idylinositol Lipid anchor. The predominant form of the ceramide is composed
of tetracosanoic acid and 4-hydroxysphinganine. Plasma membrane vesicles r
eadily shed arabinogalactan proteins by an inherent mechanism that appears
to involve a phospholipase. This finding has significance toward understand
ing the biosynthesis, localization, and function of arabinogalactan protein
s and toward stimulating other studies that may expand the currently very s
hort List of higher plant proteins found to carry such membrane lipid ancho
rs.