Proteomic studies of Toxoplasma have revealed that many proteins exhibit multiple isoforms, indicating that post-translational modifications (PTMs) are fairly common

(69). Multiple studies see more have been performed to examine the PTMs of α- and β-tubulin in Toxoplasma, as the microtubule cytoskeleton of the parasite plays an important role in host cell invasion (70). Initially, it was believed that α- and β-tubulin were only encoded by single genes in the parasite’s genome (71), such that PTMs would be the only way to supply tubulin diversity. However, the availability of genomic data from http://www.toxodb.org implies that there might be two additional genes for both α- and β-tubulin (7). Initial studies by Plessmann et al. utilized antibodies specific to various tubulin PTMs to show that Toxoplasmaα-tubulin can be acetylated and detyrosinated (removal of the last C-terminal residue, tyrosine 453). Additionally, mass spectrometry analysis revealed that the C-terminus of α-tubulin can be truncated by five amino acids and that glutamate 445 can be subjected to polyglutamylation (72). These findings were expanded upon by Xiao et al. (73), where cytoskeleton fractions were prepared from purified RH strain tachyzoites and subjected to 2DE followed by either immunoblotting buy BMN 673 with PTM-specific antibodies or identification of relevant bands with mass

spectrometry. Two β-tubulin isotypes and one α-tubulin isotype were detected from approximately 16 spots on a 2D gel. Between α- and β-tubulin, α-tubulin can undergo a wider spectrum of PTMs. The PTMs observed in the α-tubulin isotype included acetylation at lysine 40, detyrosination, polyglutamylation, methylation and C-terminal truncation of the last

two and last five amino acids. Of these modifications, only polyglutamylation Tobramycin and methylation were observed in β-tubulin. Methylation as a PTM has not been documented in tubulin previously, although Xiao et al. (73) mass spectrometry studies identified it on C-terminal α-tubulin peptides and peptides from one of the two β-tubulin isotypes. This tubulin methylation was not found in the human foreskin fibroblast host cells and may represent a specific modification for apicomplexa. As microtubules in Toxoplasma exhibit several functions that are specific to apicomplexans (gliding motility and invasion), garnering a greater understanding of the PTMs of tubulin could help to provide new therapeutic targets. The availability of a Toxoplasma reference genome sequence has been a great incentive for genomics studies, which have significantly shaped our understanding of unique cellular processes that drive Toxoplasma infection. Major progress has been made in the areas of host–parasite interaction, parasite cell division, intercellular transmission and stage differentiation.