title: A methionine synthase homolog is associated with secretory vesicles in tobacco pollen tubes.
abstract: Seven isoforms of 85 kDa polypeptides (p85) were identified as methionine synthase (MetE) homologs by partial aminoacid sequencing in tobacco pollen tube extracts. Immunocytochemistry data showed a localization of the antigen on the surface of tip-focussed post-Golgi secretory vesicles (SVs), that appear to be partially associated with microtubules (Mts). The chemical dissection of pollen tube high speed supernatant (HSS) showed that two distinct pools of MetE are present in pollen tubes, one being the more acidic isoforms sedimenting at 15S and the remaining at 4S after zonal centrifugation through a sucrose density gradient. The identification of the MetE within the pollen tube and its possible participation as methyl donor in a wide range of metabolic reactions, makes it a good subject for studies on pollen tube growth regulation.
authors.affiliation: Dipartimento di Biologia, Università degli Studi di Milano, Via Celoria 26, 20133, Milano, Italy.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Moscatelli
authors.forename: Monica
authors.initials: M
authors.lastname: Scali
authors.forename: Cristina
authors.initials: C
authors.lastname: Prescianotto-Baschong
authors.forename: Myriam
authors.initials: M
authors.lastname: Ferro
authors.forename: Jerome
authors.initials: J
authors.lastname: Garin
authors.forename: Rita
authors.initials: R
authors.lastname: Vignani
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Ciampolini
authors.forename: Mauro
authors.initials: M
authors.lastname: Cresti
mesh_terms: D013766:5-Methyltetrahydrofolate-Homocysteine S-Methyltransferase / Q000378:metabolism*; D000595:Amino Acid Sequence; D007527:Isoenzymes; D008969:Molecular Sequence Data; D010940:Plant Proteins; D011058:Pollen / Q000201:enzymology* / Q000648:ultrastructure; D022142:Secretory Vesicles / Q000201:enzymology* / Q000648:ultrastructure; D017386:Sequence Homology, Amino Acid; D014026:Nicotiana / Q000201:enzymology* / Q000648:ultrastructure
chemical_list: D007527:Isoenzymes; D010940:Plant Proteins; D013766:5-Methyltetrahydrofolate-Homocysteine S-Methyltransferase