Identification of Posttranslationally Modified 18-Kilodalton Protein from Rice as Eukaryotic Translation Initiation Factor 5A

Abstract

Using anther-derived rice (Oryza sativa 1.) cell-suspension cultures, we have identified an 18-kD protein that is posttranslationally modified by spermidine and is influenced by endogenous polyamine levels. The posttranslationally modified residue has been identified as the unusual amino acid hypusine [NC-(4-amino-2-hydroxybutyl)lysine] by reverse-phase high-performance liquid chromatography and gas chromatography-mass-spectrometry analyses. Differential labeling of the protein with labeled amines provided evidence that the butylamine moiety of spermidine is the immediate precursor of the hypusine residue in the protein. The eukaryotic translation initiation factor 5A (elF-5A) is the only known mammalian protein that undergoes a similar posttranslational modification with hypusine. The purified 18-kD protein coelectrophoreses with human translational initiation factor elF-5A in both isoelectric focusing and sodium dodecyl sulfate-polyacrylamide gels. The purified protein from rice stimulated methionylpuromycin synthesis in vitro, indicating its functional similarity to mammalian elF-5A. The results presented provide evidence that the posttranslationally modified 18-kD protein from rice containing hypusine is elF-5A and suggest the conservation of hypusinecontaining translation initiation factor elF-5A in eukaryotes.

The plant translational apparatus

“…elF5A has been isolated from rice and, like mammalian eIF5A, is a low-molecular-weight single polypeptide (Mr 18 000) [188]. eIF5A is the only protein that contains a modified lysine residue (hypusine) that is found in all eukaryotic eIF5As (see reviews [230,231]).…”

RceIF5A, encoding an eukaryotic translation initiation factor 5A in Rosa chinensis, can enhance thermotolerance, oxidative and osmotic stress resistance of Arabidopsis thaliana

“…In plants, full-length cDNA clones encoding eIF5A have been isolated from several species including alfalfa (Pay et al 1991), tobacco (Chamot and Kuhlemeier 1992), maize (Requejo and Tena 2006;Dresselhaus et al 1999), tomato (Wang et al 2001), rice (Chou et al 2004;Wang et al 2001;Mehta et al 1994), and Arabidopsis (Wang et al 2003). Suppression of DHS exhibits delayed natural senescence (Duguay et al 2007;Wang et al 2003;Wang et al 2005), indicating that eIF5A is involved in programmed cell death (PCD).…”

Oxidative stress and fluctuations of free and conjugated polyamines in the halophyte Mesembryanthemum crystallinum L. under NaCl salinity

“…As a result, such binding can modulate PA functions (Igarashi and Kashiwagi 2000;Bagni and Tassoni 2001). Such a capacity of polyamines is involved in the regulation of many cell processes, for example, protein phosphorylation (Ye et al 1994), post-transcriptional modifications of proteins (Mehta et al 1994), and conformational transition of DNA (Basu et al 1990). In addition, PAs as well as amides of hydroxycinnamic acid may be conjugated covalently to endogenous proteins, and this process is catalyzed by transglutaminases (Dondini et al 2003).…”