Identification of the proteins required for biosynthesis of diphthamide, the target of bacterial ADP-ribosylating toxins on translation elongation factor 2.
Diphthamide, a posttranslational modification of translation elongation factor 2 that is conserved in all eukaryotes and archaebacteria and is the target of diphtheria toxin, is formed in yeast by the actions of five proteins, Dph1 to -5, and a still unidentified amidating enzyme. Dph2 and Dph5 were previously identified. Here, we report the identification of the remaining three yeast proteins (Dph1, -3, and -4) and show that all five Dph proteins have either functional (Dph1, -2, -3, and -5) or sequence (Dph4) homologs in mammals. We propose a unified nomenclature for these proteins (e.g., HsDph1 to -5 for the human proteins) and their genes based on the yeast nomenclature. We show that Dph1 and Dph2 are homologous in sequence but functionally independent. The human tumor suppressor gene OVCA1, previously identified as homologous to yeast DPH2, is shown to actually be HsDPH1. We show that HsDPH3 is the previously described human diphtheria toxin and Pseudomonas exotoxin A sensitivity required gene 1 and that DPH4 encodes a CSL zinc finger-containing DnaJ-like protein. Other features of these genes are also discussed. 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.
Liu
Shihui
S
Microbial Pathogenesis Section, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
Milne
G Todd
GT
Kuremsky
Jeffrey G
JG
Fink
Gerald R
GR
Leppla
Stephen H
SH
D000244:Adenosine Diphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D016466:CHO Cells; D003001:Cloning, Molecular; D006224:Cricetinae; D004167:Diphtheria Toxin / Q000494:pharmacology*; D004351:Drug Resistance / Q000187:drug effects; D005800:Genes, Fungal / Q000235:genetics; D005816:Genetic Complementation Test; D006639:Histidine / Q000031:analogs & derivatives* / Q000096:biosynthesis* / Q000737:chemistry / Q000172:deficiency / Q000378:metabolism; D006801:Humans; D007506:Iron-Sulfur Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D015778:Minor Histocompatibility Antigens; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009154:Mutation / Q000235:genetics; D020652:Peptide Elongation Factor 2 / Q000378:metabolism*; D010802:Phylogeny; D011485:Protein Binding; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism
C121987:DPH1 protein, human; D004167:Diphtheria Toxin; C000592138:Dph1 protein, S cerevisiae; D007506:Iron-Sulfur Proteins; D015778:Minor Histocompatibility Antigens; D020652:Peptide Elongation Factor 2; D011506:Proteins; D029701:Saccharomyces cerevisiae Proteins; D025521:Tumor Suppressor Proteins; D006639:Histidine; D000244:Adenosine Diphosphate; C027527:diphthamide