title: The Arabidopsis tonoplast is almost devoid of glycoproteins with complex N-glycans, unlike the rat lysosomal membrane.
abstract: The distribution of the N-glycoproteome in integral membrane proteins of the vacuolar membrane (tonoplast) or the plasma membrane of Arabidopsis thaliana and, for further comparison, of the Rattus norvegicus lysosomal and plasma membranes, was analyzed. In silico analysis showed that potential N-glycosylation sites are much less frequent in tonoplast proteins. Biochemical analysis of Arabidopsis subcellular fractions with the lectin concanavalin A, which recognizes mainly unmodified N-glycans, or with antiserum against Golgi-modified N-glycans confirmed the in silico results and showed that, unlike the plant plasma membrane, the tonoplast is almost or totally devoid of N-glycoproteins with Golgi-modified glycans. Lysosomes share with vacuoles the hydrolytic functions and the position along the secretory pathway; however, our results indicate that their membranes had a divergent evolution. We propose that protection against the luminal hydrolases that are abundant in inner hydrolytic compartments, which seems to have been achieved in many lysosomal membrane proteins by extensive N-glycosylation of the luminal domains, has instead been obtained in the vast majority of tonoplast proteins by limiting the length of such domains.
authors.affiliation: Istituto di Biologia e Biotecnologia Agraria, CNR, Milano, Italy pedrazzini@ibba.cnr.it.
authors.forename: Emanuela
authors.initials: E
authors.lastname: Pedrazzini
authors.affiliation: Parco Tecnologico Padano, Lodi, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Caprera
authors.affiliation: Parco Tecnologico Padano, Lodi, Italy.
authors.forename: Ilaria
authors.initials: I
authors.lastname: Fojadelli
authors.affiliation: Istituto di Biologia e Biotecnologia Agraria, CNR, Milano, Italy.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Stella
authors.affiliation: Istituto di Biologia e Biotecnologia Agraria, CNR, Milano, Italy.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Rocchetti
authors.affiliation: Institute of Plant Biology, University of Zurich, Zurich, Switzerland.
authors.forename: Barbara
authors.initials: B
authors.lastname: Bassin
authors.affiliation: Institute of Plant Biology, University of Zurich, Zurich, Switzerland.
authors.forename: Enrico
authors.initials: E
authors.lastname: Martinoia
authors.affiliation: Istituto di Biologia e Biotecnologia Agraria, CNR, Milano, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Vitale
mesh_terms: D000818:Animals; D017360:Arabidopsis / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D003198:Computer Simulation; D004721:Endoplasmic Reticulum / Q000378:metabolism; D006023:Glycoproteins / Q000737:chemistry / Q000378:metabolism*; D006031:Glycosylation; D007425:Intracellular Membranes / Q000378:metabolism*; D008247:Lysosomes / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism; D008861:Microsomes / Q000378:metabolism; D009844:Oligosaccharides / Q000378:metabolism; D010455:Peptides / Q000378:metabolism; D011134:Polysaccharides / Q000378:metabolism*; D020543:Proteome / Q000378:metabolism; D051381:Rats; D014617:Vacuoles / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D006023:Glycoproteins; D008565:Membrane Proteins; D009844:Oligosaccharides; D010455:Peptides; D011134:Polysaccharides; D020543:Proteome
keywords: Asparagine-linked oligosaccharides; cell evolution; glycoproteins; integral membrane proteins; lysosome; plant vacuole; tonoplast.