Identification of the Phosphorylated Residues in TveIF5A by Mass Spectrometry

Abstract

The initiation factor eIF5A in Trichomonas vaginalis (TveIF5A) is previously shown to undergo hypusination, phosphorylation and glycosylation. Three different pI isoforms of TveIF5A have been reported. The most acidic isoform (pI 5.2) corresponds to the precursor TveIF5A, whereas the mature TveIF5A appears to be the most basic isoform (pI 5.5). In addition, the intermediary isoform (pI 5.3) is found only under polyamine-depleted conditions and restored with exogenous putrescine. We propose that differences in PI are due to phosphorylation of the TveIF5A isoforms. Here, we have identified phosphorylation sites using mass spectrometry. The mature TveIF5A contains four phosphorylated residues (S3, T55, T78 and T82). Phosphorylation at S3 and T82 is also identified in the intermediary TveIF5A, while no phosphorylated residues are found in the precursor TveIF5A. It has been demonstrated that eIF5A proteins from plants and yeast are phosphorylated by a casein kinase 2 (CK2). Interestingly, a gene encoding a protein highly similar to CK2 (TvCK2) is found in T. vaginalis, which might be involved in the phosphorylation of TveIF5A in T. vaginalis.

Bifunctional activity of deoxyhypusine synthase/hydroxylase from Trichomonas vaginalis

“…Moreover, in parasites grown in the absence of polyamines and transferred to medium with exogenous putrescine a new spot was observed that might correspond to intermediate TveIF-5A form (P2), these findings was previously observed [51]. According to previous reports, native…”

“…TveIF-5A is phosphorylated and O-glycosylated in the parasite [26,51], these modifications might result in an intermediate TveIF-5A isoform. These observations suggest that polyamines may play an essential role in the posttranslational modification of TveIF-5A by hypusination.…”

Quantitative phosphoproteomics reveals the role of the AMPK plant ortholog SnRK1 as a metabolic master regulator under energy deprivation

“…The eukaryotic translation factor eIF5A (eIF5A1, eIF5A2, and eIF5A3 in Arabidopsis), appears to be highly conserved in all eukaryotes 69 . Interestingly, the most divergent part between plants and mammals is the N-terminus, which is conserved between plants and parasites 70 71 . The N-terminus of plant eIF5As contains a Ser residue at position 2 which we found to be more phosphorylated in snrk1α1 / α2 mutant than in Col-0 wild type ( Fig.…”

Eukaryotic translation initiation factor 5A and its posttranslational modifications play an important role in proliferation and potentially in differentiation of the human enteric protozoan parasite Entamoeba histolytica

“…Secreted tyrosine sulfated-eIF5A mediates oxidative stress-induced apoptosis by acting as a pro-apoptotic ligand [22]. It has also been reported in T. vaginalis that eIF5A is phosphorylated at serine 2 in a stretch of the consensus sequence present at the amino terminus (MSSAEEEV) [44]. A similar sequence (MSSNGSDN) is also present at the amino terminus of EheIF5A2, but not in EheIF5A1, suggesting that EheIF5A2 may be phosphorylated (Fig 2B).…”