Disease relevance of diphthamide

• The results strongly suggest that the cellular transferase is a mono(ADP-ribosyl)transferase, which ADP-ribosylates the same diphthamide residue of EF-2 as does fragment A and Pseudomonas toxin A [1].
• Elongation factor 2 (EF-2) from S. acidocaldarius was cloned in E. coli and the expressed gene product was used in order to adsorb all anti-EF-2 antibodies which do not contain the ADP-ribosyl group within their epitopes, as E. coli is unable to synthesize the ADP-ribosyl acceptor diphthamide [2].
• Modulation of diphthamide synthesis by 5'-deoxy-5'-methylthioadenosine in murine lymphoma cells [3].

High impact information on diphthamide

• We demonstrate that DESR1 is required for the first step in the posttranslational modification of elongation factor-2 at His(715) that yields diphthamide, the target site for ADP ribosylation by DT and ETA [4].
• Retroviral insertional mutagenesis identifies a small protein required for synthesis of diphthamide, the target of bacterial ADP-ribosylating toxins [4].
• Yeast dph2 mutants are resistant to diphtheria toxin, which catalyses ADP ribosylation of EF-2 at diphthamide [5].
• Of the proteins required for diphthamide synthesis, Dph3 is the smallest, containing only 82 residues [6].
• The evolutionary conservation of the complex diphthamide biosynthesis pathway throughout eukaryotes implies a key role for diphthamide in normal cellular physiology [6].

Chemical compound and disease context of diphthamide

• The diphthamide at the tip of domain IV, which is the target for diphtheria toxin and Pseudomonas aeruginosa exotoxin A, contains a covalently attached ADP-ribose that functions as a very potent inhibitor of the factor [7].

Biological context of diphthamide

• A null mutation of the chromosomal DPH5 gene did not affect cell viability, in agreement with other studies indicating that diphthamide is not required for cell survival [8].
• All three amino acid substitutions prevented the biosynthesis of diphthamide [9].
• Acid hydrolysis of diphthamide yields amino acid X for which we propose the trivial name diphthine [10].
• Elongation factor 2 mutants deficient in diphthamide formation show temperature-sensitive cell growth [11].
• We have identified a cDNA corresponding to the sequence of the known gene diphthamide biosynthesis protein 2-like (DPH2L) [12].

Anatomical context of diphthamide

• Thus, beef liver and pyBHK mono(ADP-ribosyl)transferases both modify the diphthamide residue of EF-2, in a manner identical to diphtheria toxin fragment A and Pseudomonas toxin A. These results suggest the cellular enzyme is probably ubiquitous among eukaryotic cells [13].
• These results suggest that histidine-715 is essential for the translocase activity of EF-2 and that the region around diphthamide functions in recognition of, and/or binding to ribosomes [14].
• In the present experiments, we have analyzed the effects of MeSAdo on diphthamide synthesis in a MeSAdo phosphorylase-deficient mutant murine lymphoma cell line (R1.1, clone H3) [3].

Associations of diphthamide with other chemical compounds

• The amino acid diphthamide is a complex post-translational derivative of histidine that exists in eukaryotic and Archaebacterial elongation factor 2 (EF-2) [15].
• In addition, yeast and mammalian EF-2 share identical sequences at two critical functional sites: (i) the domain containing the histidine residue that is modified to diphthamide and (ii) the threonine residue that is specifically phosphorylated in vivo in mammalian cells by calmodulin-dependent protein kinase III, also known as EF-2 kinase [16].
• Diphtheria toxin inactivates protein synthesis elongation factor 2 by attaching ADP-ribose to an unusual post-translational amino acid derivative, diphthamide, in the factor [17].

Gene context of diphthamide

• Diphthamide synthesis in Saccharomyces cerevisiae: structure of the DPH2 gene [18].
• The physiological function of diphthamide and the basis of its ubiquity remain a mystery, but evidence is presented that Dph1 to -3 function in vivo as a protein complex in multiple cellular processes [19].
• This highly conserved gene has significant sequence similarity to a yeast gene of unknown function and to one of the yeast enzymes in the diphthamide synthetic pathway, DPH2, that has a role in global protein synthesis regulation [20].
• Gene trap mutagenesis-based forward genetic approach reveals that the tumor suppressor OVCA1 is a component of the biosynthetic pathway of diphthamide on elongation factor 2 [21].
• Recognition of elongation factor 2 by diphtheria toxin is not solely defined by the presence of diphthamide [22].

Analytical, diagnostic and therapeutic context of diphthamide

• An enzyme-linked immunosorbent assay for the association of the catalytic domain of diphthamide-specific ribosyltransferases to eukaryotic elongation factor-2 [23].

References