The second cholera toxin, Zot, and its plasmid-encoded and phage-encoded homologues constitute a group of putative ATPases with an altered purine NTP-binding motif.
It is shown that the second cholera toxin, Zot, ORF3 product of Pseudomonas plasmid pKB740, and ORF424 product of bacteriophage Pf1 are a group of closely related proteins containing a modified version of the purine NTP-binding motif, with a drastic substitution of tyrosine for a conserved glycine. They are distantly but reliably related to the product of gene I of filamentous bacteriophages which is a putative ATPase containing the classical NTP-binding motif and is involved in bacteriophage assembly and exit from the bacterial cell. Hydropathy analysis suggests that the Zot and gene I product may have a similar transmembrane topology. It is hypothesized that Zot may possess ATPase activity and modify the membrane structure of its target cells in an ATP-dependent fashion. Genes for Zot and the related protein of pKB740 are likely to have evolved from gene I of a Pf1-like bacteriophage.
Koonin
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National Center for Biotechnology Information, National Library of Medicine, NIH, Bethesda, MD 20894.
D000251:Adenosine Triphosphatases / Q000235:genetics*; D000595:Amino Acid Sequence; D001665:Binding Sites; D002352:Carrier Proteins / Q000235:genetics*; D002772:Cholera Toxin / Q000235:genetics*; D004731:Endotoxins; D005798:Genes, Bacterial; D005814:Genes, Viral; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D010957:Plasmids; D011487:Protein Conformation; D017386:Sequence Homology, Amino Acid; D012984:Software; D014734:Vibrio cholerae / Q000235:genetics*
D002352:Carrier Proteins; D004731:Endotoxins; C077728:zonula occludens toxin, Vibrio cholerae; D002772:Cholera Toxin; D000251:Adenosine Triphosphatases