title: Post-translational modifications to Toxoplasma gondii alpha- and beta-tubulins include novel C-terminal methylation.
abstract: Toxoplasma gondii is an apicomplexan of both medical and veterinary importance which is classified as an NIH Category B priority pathogen. It is best known for its ability to cause congenital infection in immune competent hosts and encephalitis in immune compromised hosts. The highly stable and specialized microtubule-based cytoskeleton participates in the invasion process. The genome encodes three isoforms of both alpha- and beta-tubulin and we show that the tubulin is extensively altered by specific post-translational modifications (PTMs) in this paper. T. gondii tubulin PTMs were analyzed by mass spectrometry and immunolabeling using specific antibodies. The PTMs identified on alpha-tubulin included acetylation of Lys40, removal of the last C-terminal amino acid residue Tyr453 (detyrosinated tubulin) and truncation of the last five amino acid residues. Polyglutamylation was detected on both alpha- and beta-tubulins. An antibody directed against mammalian alpha-tubulin lacking the last two C-terminal residues (Delta2-tubulin) labeled the apical region of this parasite. Detyrosinated tubulin was diffusely present in subpellicular microtubules and displayed an apparent accumulation at the basal end. Methylation, a PTM not previously described on tubulin, was also detected. Methylated tubulins were not detected in the host cells, human foreskin fibroblasts, suggesting that this may be a modification specific to the Apicomplexa.
authors.affiliation: Departments of Pathology, Laboratory for Macromolecular Analysis and Proteomics, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
authors.forename: Hui
authors.initials: H
authors.lastname: Xiao
authors.forename: Kamal
authors.initials: K
authors.lastname: El Bissati
authors.forename: Pascal
authors.initials: P
authors.lastname: Verdier-Pinard
authors.forename: Berta
authors.initials: B
authors.lastname: Burd
authors.forename: Hongshan
authors.initials: H
authors.lastname: Zhang
authors.forename: Kami
authors.initials: K
authors.lastname: Kim
authors.forename: Andras
authors.initials: A
authors.lastname: Fiser
authors.forename: Ruth Hogue
authors.initials: RH
authors.lastname: Angeletti
authors.forename: Louis M
authors.initials: LM
authors.lastname: Weiss
mesh_terms: D000107:Acetylation; D000595:Amino Acid Sequence; D003599:Cytoskeleton / Q000737:chemistry / Q000378:metabolism*; D015180:Electrophoresis, Gel, Two-Dimensional; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism; D008745:Methylation; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D010455:Peptides; D020033:Protein Isoforms / Q000737:chemistry / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D040901:Proteomics / Q000379:methods; D016415:Sequence Alignment; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D014122:Toxoplasma / Q000737:chemistry / Q000378:metabolism*; D014404:Tubulin / Q000737:chemistry / Q000378:metabolism*
chemical_list: D008565:Membrane Proteins; D010446:Peptide Fragments; D010455:Peptides; D020033:Protein Isoforms; D014404:Tubulin; C097188:polyglutamine