Some properties of the lectin from Datura stramonium (thorn-apple) and the nature of its glycoprotein linkages

Abstract

The lectin from Datura stramonium (thorn-apple; Solanaceae) has been purified by affinity chromatography and shown to be a glycoprotein containing about 40% (w/w) of carbohydrate. The most abundant amino acids are hydroxyproline, cystine, glycine and serine. Results obtained by gel filtration in 6m-guanidinium chloride on Sepharose 4B suggest that it has a subunit mol.wt. of about 30000 and that it probably associates into dimers. The lectin is inhibited specifically by chitin oligosaccharides and bacterial-cell-wall oligosaccharides, but only weakly by N-acetylglucosamine. Glycopeptides from soya-bean (Glycine max) lectin and fetuin are also strong inhibitors of Datura lectin, indicating that it interacts with internal N-acetylglucosamine residues. Its specificity is similar to, but not identical with, that of potato (Solanum tuberosum) lectin. After prolonged proteolytic digestion of reduced and S-carboxymethylated or S-aminoethylated derivatives of the lectin, glycopeptides of mol.wt. of about 18000 were isolated. The glycopeptides contained all the carbohydrate and hydroxyproline of the original glycoprotein, and lesser amounts of serine, S-carboxymethylcysteine and other amino acids. The arabinose residues of the glycoprotein are present as beta-l-arabinofuranosides linked to the polypeptide chain through the hydroxyproline residues, and can be removed by mild acid treatment; the ratio of arabinose to hydroxyproline is 3.4:1. Some of the serine residues of the polypeptide chain are substituted with one or two alpha-galactopyranoside residues, most of which can be removed by the action of alpha-galactosidase. The galactose residues are more easily removed from the acid-treated glycopeptide (from which arabinose has been removed) than from the complete glycopeptide, indicating a steric hindrance of the galactosidase action by the adjacent chains of arabinosides. There is a slow release of galactose residues by a process of beta-elimination in 0.5m-NaOH (pH13.7) from the complete glycopeptide, and a fairly rapid release of galactose by this process from the acid-treated glycopeptide, which lacks arabinose. This is probably due to the inhibitory effect of the negative charge on the adjacent arabinofuranoside residues. The similarities and differences between the lectins from Datura and potato are discussed, as are their structural resemblance to glycopeptides that have been isolated from plant cell walls.

Chlamydomonas agglutinin is a hydroxyproline-rich glycoprotein

“…Noteworthy is the high content of hydroxyproline (=12%) and serine (--10%). These two amino acids serve as attachment points for oligosaccharide chains in cell wall glycopolypeptides of Chlamydomonas (13) and higher plants ( [14][15][16], in plant arabinogalactan proteins (17), and in the wall-associated lectins of the Solanacae (18)(19)(20)(21)(22)(23). Arabinans linked to hydroxyproline in plant cell wall proteins are thought to reinforce the polyproline II helical conformation (24, 25; G. J.…”

“…The self-assembly of Chlamydomonas wall glycoproteins into a crystalline pseudowall (42) undoubtedly involves molecular recognition, making it attractive to speculate that the sexual agglutinin has evolved from such structural proteins to perform an intercellular recognition or adhesion function. Because plant lectins also contain hydroxyproline-rich domains (18)(19)(20)(21)(22)(23), the Chlamydomonas agglutinin may well also prove to have lectin activity, with its stiff domain 2 serving to display more distal recognition domains to gametes of the opposite mating type. The presence of a collagen-like tail on the asymmetric form of-acetylcholinesterase of vertebrate nervous systems (43) and the crosslinking properties of the collagen IV component of the basal lamina (44) suggest that a similar molecular design may have been adopted more generally by proteins that function to mediate cell-cell interactions.…”

Polyproline II Confirmation in the Protein Component of Arabinogalactan-Protein from Lolium multiflorum

“…The hydroxyproline-rich cell wall glycoprotein from carrot has been shown by circular dichrometry to exist in the polyproline II conformation (17), which consists of a lefthanded helix of three residues per turn and a rise for residue of 0.31 nm (15). Based on optical rotary dispersion measurements, it has been suggested that lectins of the Solanaceae also contain polyproline II conformation (1,7). In was isolated from the medium by affinity chromatography on myeloma protein J539-Sepharose (3).…”

A High Proportion of Hybridomas Raised to a Plant Extract Secrete Antibody to Arabinose or Galactose

“…Potato and Datura lectins are poor inhibitors of all the antibodies, consistent with their known low content of i-galactose which is in the a-configuration (2,6).These lectins have a high content of L-arabinose which is mainly present as tri-and tetra-arabinosyl side chains. The anomeric linkages are in the ,-configuration except for the terminal nonreducing arabinosyl group of the tetra arabinosyl side chains which are in the a-configuration (2,6).…”

“…The anomeric linkages are in the ,-configuration except for the terminal nonreducing arabinosyl group of the tetra arabinosyl side chains which are in the a-configuration (2,6).…”