Diphthamide is a post-translationally modified

histidine Histidine (symbol His or H) is an essential amino acid that is used in the biosynthesis of proteins. It contains an α-amino group (which is in the protonated –NH3+ form under biological conditions), a carboxylic acid group (which is in the de ...

amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha am ...

found in archaeal and eukaryotic elongation factor 2 (eEF-2).

Structure

Diphthamide is proposed to be a 2- -carboxyamido-3-(trimethylammonio)propylistidine. Though this structure has been confirmed by

X-ray crystallography X-ray crystallography is the experimental science determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to diffract into many specific directions. By measuring the angles ...

, its stereochemistry is uncertain.

Biological function

Diphthamide ensures translation fidelity. The presence or absence of diphthamide is known to affect

NF-κB Nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) is a protein complex that controls transcription of DNA, cytokine production and cell survival. NF-κB is found in almost all animal cell types and is involved in cellular ...

or death receptor pathways.

Biosynthesis

Diphthamide is biosynthesized from histidine and ''S''-adenosyl methionine.

References

{{Reflist Amino acids Imidazoles Quaternary ammonium compounds Post-translational modification Zwitterions