title: Inhibition of the adenylylation of liver plasma membrane-bound proteins by plant and mammalian lectins.
abstract: Liver plasma membrane contains four major (130-kDa, 120-kDa, 110-kDa and 100-kDa) sialic acid-containing glycopolypeptides that are able to undergo adenylylation, as well as phosphorylation (San José et al. (1990) J. Biol. Chem. 265; 20653-20661). To gain insight into the regulation of these processes, lectins are employed to probe the extent of influence of their interaction with membrane fractions for these reactions. We demonstrate that the beta-galactoside-specific lectins from bovine heart and mistletoe at low concentrations inhibit the adenylylation of this set of plasma membrane glycopolypeptides. The extent of phosphorylation of these polypeptides is also reduced although to a lesser degree. Concanavalin A, too, inhibits the adenylylation of the plasma membrane glycopolypeptides, although higher concentrations of this lectin were required, whereas wheat germ lectin has only a very small inhibitory effect. The adenylylable polypeptides were isolated by concanavalin A-agarose chromatography upon elution with mannose. In agreement with this result, control experiments with a panel of neoglycoproteins indicate that mannose residues appear to be required for the concanavalin A-induced inhibition of the adenylylation. Neoglycoproteins containing mannose 6-phosphate, lactose, fucose, or sialic acid instead of mannose lack the ability to protect the adenylylation from the inhibitory action of concanavalin A. In contrast, none of the above-mentioned neoglycoproteins, nor asialofetuin, nor galactose-containing saccharides protect the adenylylation against the inhibitory effect of both the mistletoe and bovine heart lectins, emphasizing the importance of either high affinity carbohydrate ligands in the overall process, or other ligand sites for the lectins beside carbohydrates to affect the regulation of the adenylylation system.
authors.affiliation: Instituto de Investigaciones Biomédicas, Consejo Superior de Investigaciones Científicas, Madrid, Spain.
authors.forename: E
authors.initials: E
authors.lastname: San José
authors.forename: E
authors.initials: E
authors.lastname: Villalobo
authors.forename: H J
authors.initials: HJ
authors.lastname: Gabius
authors.forename: A
authors.initials: A
authors.lastname: Villalobo
mesh_terms: D000225:Adenine / Q000378:metabolism*; D000818:Animals; D001212:Asialoglycoproteins / Q000378:metabolism; D002417:Cattle; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002846:Chromatography, Affinity; D003208:Concanavalin A / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D060748:Fetuins; D006020:Glycopeptides / Q000378:metabolism; D006023:Glycoproteins / Q000096:biosynthesis; D066298:In Vitro Techniques; D037102:Lectins / Q000494:pharmacology*; D008099:Liver / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D008297:Male; D008358:Mannose / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism; D019158:N-Acetylneuraminic Acid; D010766:Phosphorylation; D037121:Plant Lectins; D028321:Plant Preparations; D010940:Plant Proteins; D010944:Plants / Q000378:metabolism; D011506:Proteins / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D054790:Ribosome Inactivating Proteins, Type 2; D012794:Sialic Acids / Q000378:metabolism; D014118:Toxins, Biological / Q000378:metabolism; D000509:alpha-Fetoproteins / Q000378:metabolism
chemical_list: D001212:Asialoglycoproteins; D060748:Fetuins; D006020:Glycopeptides; D006023:Glycoproteins; D037102:Lectins; D037121:Plant Lectins; D028321:Plant Preparations; D010940:Plant Proteins; D011506:Proteins; D054790:Ribosome Inactivating Proteins, Type 2; D012794:Sialic Acids; D014118:Toxins, Biological; D000509:alpha-Fetoproteins; C017029:asialofetuin; C009674:ribosome inactivating protein, Viscum; D003208:Concanavalin A; D019158:N-Acetylneuraminic Acid; D000225:Adenine; D008358:Mannose