title: Identification of a novel family of 70 kDa microtubule-associated proteins in Arabidopsis cells.
abstract: Most plant microtubule-associated proteins (MAPs) have homologues across the phylogenetic spectrum. To find potential plant-specific MAPs that will have evaded bioinformatic searches we devised a low stringency method for isolating proteins from an Arabidopsis cell suspension on endogenous taxol-microtubules. By tryptic peptide mass fingerprinting we identified 55 proteins that were enriched on taxol-microtubules. Amongst a range of known MAPs, such as kinesins, MAP65 isoforms and MOR1, we detected 'unknown' 70 kDa proteins that belong to a family of five closely related Arabidopsis proteins having no known homologues amongst non-plant organisms. To verify that AtMAP70-1 associates with microtubules in vivo, it was expressed as a GFP fusion. This confirmed that the protein decorates all four microtubule arrays in both transiently infected Arabidopsis and stably transformed tobacco BY-2 suspension cells. Microtubule-directed drugs perturbed the localization of AtMAP70-1 but cytochalasin D did not. AtMAP70-1 contains four predicted coiled-coil domains and truncation studies identified a central domain that targets the fusion protein to microtubules in vivo. This study therefore introduces a novel family of plant-specific proteins that interact with microtubules.
authors.affiliation: Department of Cell and Developmental Biology, John Innes Centre, Norwich NR4 7UH, UK.
authors.forename: Andrey V
authors.initials: AV
authors.lastname: Korolev
authors.forename: Jordi
authors.initials: J
authors.lastname: Chan
authors.forename: Mike J
authors.initials: MJ
authors.lastname: Naldrett
authors.forename: John H
authors.initials: JH
authors.lastname: Doonan
authors.forename: Clive W
authors.initials: CW
authors.lastname: Lloyd
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000737:chemistry*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000302:isolation & purification*; D018506:Gene Expression Regulation, Plant; D008869:Microtubule-Associated Proteins / Q000737:chemistry / Q000302:isolation & purification*; D008969:Molecular Sequence Data; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
chemical_list: D029681:Arabidopsis Proteins; D008869:Microtubule-Associated Proteins