title: C3larvin toxin, an ADP-ribosyltransferase from Paenibacillus larvae.
abstract: C3larvin toxin was identified by a bioinformatic strategy as a putative mono-ADP-ribosyltransferase and a possible virulence factor from Paenibacillus larvae, which is the causative agent of American Foulbrood in honey bees. C3larvin targets RhoA as a substrate for its transferase reaction, and kinetics for both the NAD(+) (Km = 34 ± 12 μm) and RhoA (Km = 17 ± 3 μm) substrates were characterized for this enzyme from the mono-ADP-ribosyltransferase C3 toxin subgroup. C3larvin is toxic to yeast when expressed in the cytoplasm, and catalytic variants of the enzyme lost the ability to kill the yeast host, indicating that the toxin exerts its lethality through its enzyme activity. A small molecule inhibitor of C3larvin enzymatic activity was discovered called M3 (Ki = 11 ± 2 μm), and to our knowledge, is the first inhibitor of transferase activity of the C3 toxin family. C3larvin was crystallized, and its crystal structure (apoenzyme) was solved to 2.3 Å resolution. C3larvin was also shown to have a different mechanism of cell entry from other C3 toxins.
authors.affiliation: From the Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario N1G 2W1, Canada.
authors.forename: Daniel
authors.initials: D
authors.lastname: Krska
authors.affiliation: From the Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario N1G 2W1, Canada.
authors.forename: Ravikiran
authors.initials: R
authors.lastname: Ravulapalli
authors.affiliation: the Computational Biology Center, Memorial Sloan-Kettering Cancer Center, New York, New York 10065, and the Department of Systems Biology, Harvard Medical School, Boston, Massachusetts 02115.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Fieldhouse
authors.affiliation: From the Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario N1G 2W1, Canada.
authors.forename: Miguel R
authors.initials: MR
authors.lastname: Lugo
authors.affiliation: From the Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario N1G 2W1, Canada, rmerrill@uoguelph.ca.
authors.forename: A Rod
authors.initials: AR
authors.lastname: Merrill
mesh_terms: D036002:ADP Ribose Transferases / Q000737:chemistry*; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry*; D001905:Botulinum Toxins / Q000737:chemistry; D002384:Catalysis; D002942:Circular Dichroism; D019295:Computational Biology; D003460:Crystallization; D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000737:chemistry; D020128:Inhibitory Concentration 50; D008969:Molecular Sequence Data; D009243:NAD / Q000737:chemistry; D056507:Paenibacillus / Q000201:enzymology*; D011485:Protein Binding; D011487:Protein Conformation; D017386:Sequence Homology, Amino Acid; D014118:Toxins, Biological / Q000737:chemistry; D037521:Virulence Factors; D020742:rhoA GTP-Binding Protein / Q000737:chemistry*
chemical_list: D001426:Bacterial Proteins; D014118:Toxins, Biological; D037521:Virulence Factors; D009243:NAD; D006160:Guanosine Triphosphate; D036002:ADP Ribose Transferases; D001905:Botulinum Toxins; D020742:rhoA GTP-Binding Protein
keywords: ADP-ribosylation; ADP-ribosyltransferase Inhibitor; Bacterial Toxin; Bioinformatics; C3 Toxins; Enzyme Kinetics; Fluorescence; X-ray Crystallography