Post-translational modifications to Toxoplasma gondii alpha- and beta-tubulins include novel C-terminal methylation.
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.
Xiao
Hui
H
Departments of Pathology, Laboratory for Macromolecular Analysis and Proteomics, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
El Bissati
Kamal
K
Verdier-Pinard
Pascal
P
Burd
Berta
B
Zhang
Hongshan
H
Kim
Kami
K
Fiser
Andras
A
Angeletti
Ruth Hogue
RH
Weiss
Louis M
LM
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*
D008565:Membrane Proteins; D010446:Peptide Fragments; D010455:Peptides; D020033:Protein Isoforms; D014404:Tubulin; C097188:polyglutamine