This entry includes diphthamide synthesis DPH1 from eukaryotes and archaea and DPH2 from archaea.Archaeal and eukaryotic translation elongation factor 2 (EF-2) contain a unique posttranslationally modified histidine residue called diphthamide, which become the target for ADP-ribosylation by diphtheria toxin []. DPH1 catalyzes the first step of diphthamide biosynthesis and is required for the modification of EF-2 []. The human DPH1 is also known as OVCA1 (for ovarian cancer gene 1), a tumour suppressor gene that plays a crucial role in the regulation of cell proliferation, embryonic development, and tumorigenesis [].
Archaeal and eukaryotic translation elongation factor 2 contain a unique posttranslationally modified histidine residue called diphthamide, the target of the diphtheria toxin. Diphtheria toxin inhibits eukaryotic protein synthesis by ADP-ribosylating diphthamide in EF2 [].Members of this family include 2-(3-amino-3-carboxypropyl)histidine synthase subunit 1/2 (also known as Diphtheria toxin resistance protein 1/2, DPH 1/2), which are involved in the first step of diphthamide synthesis [, ]. Archaeal DPHs are more similar to eukaryotic DPH1 than to DPH2 [].
Diphthamide is a unique post-translationally modified histidine residue found only in translation elongation factor 2 (eEF-2). It is conserved from archaea to humans and serves as the target for diphteria toxin and Pseudomonas exotoxin A. These two toxins catalyse the transfer of ADP-ribose to diphtamide on eEF-2, thus inactivating eEF-2, halting cellular protein synthesis, and causing cell death []. The biosynthesis of diphtamide is dependent on at least five proteins, DPH1 to -5, and a still unidentified amidating enzyme. DPH3 and DPH4 share a conserved region, which encode a putative zinc finger, the DPH-type or CSL-type (after the the final conserved cysteine of the zinc finger and the next two residues) MB domain contains a Cys-X-Cys...Cys-X2-Cys motif which tetrahedrically coordinates both Fe and Zn. The Fe containing DPH-type MBD has an electron transfer activity [, , , , , ].This entry includes DPH3, DPH4 and their homologues.
Diphthamide is a unique post-translationallymodified histidine residue found only in translation elongation factor 2 (eEF-2). It is conserved from archaea to humans and serves as the target for diphteria toxin and Pseudomonas exotoxin A. These two toxins catalyse the transfer of ADP-ribose to diphtamide on eEF-2, thus inactivating eEF-2, halting cellular protein synthesis, and causing cell death []. The biosynthesis of diphtamide is dependent on at least five proteins, DPH1 to -5, and a still unidentified amidating enzyme. DPH3 and DPH4 share a conserved region, which encode a putative zinc finger, the DPH-type or CSL-type (after the the final conserved cysteine of the zinc finger and the next two residues) MB domain contains a Cys-X-Cys...Cys-X2-Cys motif which tetrahedrically coordinates both Fe and Zn. The Fe containing DPH-type MBD has an electron transfer activity [, , , , , ].This entry represents the DPH-type metal binding domain consists of a three-stranded β-sandwich with one sheet comprising two parallel strands: (i) β1 and (ii) β6 and one antiparallel strand: β5. The second sheet in the β-sandwich is comprised of strands β2, β3, and β4 running anti-parallel to each other. The two β-sheets are separated by a short stretch α-helix. It can be found in proteins such as DPH3 and DPH4. This domain is also found associated with N-terminal domain of heat shock protein DnaJ domain [, , ].
Diphthamide is the name given to a unique post-translationally modified histidine residue in archaeal and eukaryotic translation elongation factor 2. Thismodified histidine is target of diphtheria toxin, which inhibits eukaryotic protein synthesis by ADP-ribosylating diphthamide in EF2 [].The diphthamide synthesis DPH1/DPH2 enzymes which catalyse the first step in diphthamide biosynthesis. Archaeal DPHs are more similar to eukaryotic DPH1 than to DPH2 [].Available structural information on PhDph2 reveals that this enzyme is a homodimer and that each monomer comprises three domains which share the same overall fold. The basic domain fold is a four-stranded parallel β-sheet with three flanking α-helices (or two α-helices and one 3(10) helix in the case of domain 2). The two β-sheets in domain 1 and 2 each contain an additional β-strand that is antiparallel to the rest of the β-sheet. Domains 2 and 3 have two additional α-helices. Domain 1 of one monomer and domain 3 of the adjacent monomer form the dimer interface, creating an extended nine-stranded β-sheet. The domain folds and their arrangement resemble the structure of quinolinate synthase but the orientations of the domains with respect to each other are different in the two enzymes. Three conserved cysteine residues (Cys59, Cys163 and Cys287), each coming from a different structural domain, are clustered together in the centre of the PhDph2 monomers. All three cysteine residues are conserved in eukaryotic DPH1s. The first and third cysteine residues are conserved in eukaryotic DPH2s [].This superfamily represents the domain 2 found in diphthamide synthesis DPH1/DPH2 enzymes.
Diphthamide is the name given to a unique post-translationally modified histidine residue in archaeal and eukaryotic translation elongation factor 2. This modified histidine is target of diphtheria toxin, which inhibits eukaryotic protein synthesis by ADP-ribosylating diphthamide in EF2 [].The diphthamide synthesis DPH1/DPH2 enzymes which catalyse the first step in diphthamide biosynthesis. Archaeal DPHs are more similar to eukaryotic DPH1 than to DPH2 [].Available structural information on PhDph2 reveals that this enzyme is a homodimer and that each monomer comprises three domains which share the same overall fold. The basic domain fold is a four-stranded parallel β-sheet with three flanking α-helices (or two α-helices and one 3(10) helix in the case of domain 2). The two β-sheets in domain 1 and 2 each contain an additional β-strand that is antiparallel to the rest of the β-sheet. Domains 2 and 3 have two additional α-helices. Domain 1 of one monomer and domain 3 of the adjacent monomer form the dimer interface, creating an extended nine-stranded β-sheet. The domain folds and their arrangement resemble the structure of quinolinate synthase but the orientations of the domains with respect to each other are different in the two enzymes. Three conserved cysteine residues (Cys59, Cys163 and Cys287), each coming from a different structural domain, are clustered together in the centre of the PhDph2 monomers. All three cysteine residues are conserved in eukaryotic DPH1s. The first and third cysteine residues are conserved in eukaryotic DPH2s [].This superfamily represents the domain 1 found in diphthamide synthesis DPH1/DPH2 enzymes.
Diphthamide is the name given to a unique post-translationally modified histidine residue in archaeal and eukaryotic translation elongation factor 2. This modified histidine is target of diphtheria toxin, which inhibits eukaryotic protein synthesis by ADP-ribosylating diphthamide in EF2 [].The diphthamide synthesis DPH1/DPH2 enzymes which catalyse the first step in diphthamide biosynthesis. Archaeal DPHs are more similar to eukaryotic DPH1 than to DPH2 [].Available structural information on PhDph2 reveals that this enzyme is a homodimer and that each monomer comprises three domains which share the same overall fold. The basic domain fold is a four-stranded parallel β-sheet with three flanking α-helices (or two α-helices and one 3(10) helix in the case of domain 2). The two β-sheets in domain 1 and 2 each contain an additional β-strand that is antiparallel to the rest of the β-sheet. Domains 2 and 3 have two additional α-helices. Domain 1 of one monomer and domain 3 of the adjacent monomer form the dimer interface, creating an extended nine-stranded β-sheet. The domain folds and their arrangementresemble the structure of quinolinate synthase but the orientations of the domains with respect to each other are different in the two enzymes. Three conserved cysteine residues (Cys59, Cys163 and Cys287), each coming from a different structural domain, are clustered together in the centre of the PhDph2 monomers. All three cysteine residues are conserved in eukaryotic DPH1s. The first and third cysteine residues are conserved in eukaryotic DPH2s [].This superfamily represents the domain 3 found in diphthamide synthesis DPH1/DPH2 enzymes.
