title: Exchange of a single amino acid switches the substrate properties of RhoA and RhoD toward glucosylating and transglutaminating toxins.
abstract: Rho GTPases are the preferred targets of various bacterial cytotoxins, including Clostridium difficile toxins A and B, Clostridium sordellii lethal toxin, the cytotoxic necrotizing factors (CNF1) from Escherichia coli, and the dermonecrotizing toxin (DNT) from Bordetella species. The toxins inactivate or activate specific sets of Rho GTPases by mono-O-glucosylation and deamidation/transglutamination, respectively. Here we studied the structural basis of the recognition of RhoA, which is modified by toxin B, CNF1, and DNT, in comparison with RhoD, which is solely a substrate for lethal toxin. We found that a single amino acid residue in RhoA and RhoD defines the substrate specificity for toxin B and lethal toxin. Change of serine 73 to phenylalanine in RhoA turned RhoA into a substrate for lethal toxin. Accordingly, change of the equivalently positioned phenylalanine 85 in RhoD with serine allowed glucosylation by toxin B. Comparable results were achieved with the Rho-activating and transglutaminating enzymes CNF1 and DNT. Here, amino acid glutamate 64 of RhoA and the equivalent aspartate 76 of RhoD define substrate specificity for CNF1 and DNT, respectively. These data indicate that single amino acid residues located in the switch II region of Rho proteins determine enzyme specificity for diverse bacterial toxins.
authors.affiliation: Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Albert-Ludwigs-Universität Freiburg, D-79104 Freiburg, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Jank
authors.forename: Ulrike
authors.initials: U
authors.lastname: Pack
authors.forename: Torsten
authors.initials: T
authors.lastname: Giesemann
authors.forename: Gudula
authors.initials: G
authors.lastname: Schmidt
authors.forename: Klaus
authors.initials: K
authors.lastname: Aktories
mesh_terms: D000595:Amino Acid Sequence; D001224:Aspartic Acid / Q000737:chemistry; D001427:Bacterial Toxins; D003013:Clostridium / Q000378:metabolism*; D020558:GTP Phosphohydrolases / Q000737:chemistry; D005947:Glucose / Q000737:chemistry*; D008969:Molecular Sequence Data; D010649:Phenylalanine / Q000737:chemistry; D017386:Sequence Homology, Amino Acid; D012694:Serine / Q000737:chemistry; D013379:Substrate Specificity; D011503:Transglutaminases / Q000737:chemistry; D020741:rho GTP-Binding Proteins / Q000737:chemistry / Q000502:physiology*; D020742:rhoA GTP-Binding Protein / Q000737:chemistry / Q000502:physiology*
chemical_list: D001427:Bacterial Toxins; D001224:Aspartic Acid; D012694:Serine; D010649:Phenylalanine; D011503:Transglutaminases; D020558:GTP Phosphohydrolases; D020741:rho GTP-Binding Proteins; D020742:rhoA GTP-Binding Protein; D005947:Glucose