Английская Википедия:Diphthamide

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Diphthamide is a post-translationally modified histidine amino acid found in archaeal and eukaryotic elongation factor 2 (eEF-2).

Dipthamide is named after the toxin produced by the bacterium Corynebacterium diphtheriae, which targets diphthamide.[1] Besides this toxin, it is also targeted by exotoxin A from Pseudomonas aeruginosa.[1][2] It is the only target of these toxins.[2]

Structure and biosynthesis

Diphthamide is proposed to be a 2-[3-carboxyamido-3-(trimethylammonio)propyl]histidine. Though this structure has been confirmed by X-ray crystallography, its stereochemistry is uncertain.[1][3]

Diphthamide is biosynthesized from histidine and S-adenosyl methionine (SAM).[1] The side chain bound to imidazole group and all methyl groups come from SAM. The whole synthesis takes place in three steps:[1]

  • transfer of 3-amino-3-carboxylpropyl group from SAM
  • transfer of three methyl groups from SAM – synthesis of diphtine
  • amidation – synthesis of diphthamide

In eukaryotes, this biosynthetic pathway contains a total of 7 genes (Dph1-7).[1]

Biological function

Diphthamide ensures translation fidelity.[1]

The presence or absence of diphthamide is known to affect NF-κB or death receptor pathways.[4]

References

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