ADP ribosylation of Arg41 of Rap by ExoS inhibits the ability of Rap to interact with its guanine nucleotide exchange factor, C3G.
ExoS is a bifunctional type III cytotoxin that is secreted by Pseudomonas aeruginosa. The N-terminal domain comprises a RhoGAP activity, while the C-terminal domain comprises a ADP-ribosyltransferase activity. Previous studies showed that ExoS ADP ribosylated Ras at Arg41 which interfered with the ability of Ras to interact with its guanine nucleotide exchange factor. Rap and Ras share considerable primary amino acid homology, including Arg41. In this study, we report that ExoS ADP ribosylates Rap1b at Arg41 and that ADP ribosylation of Arg41 inhibits the ability of C3G to stimulate guanine nucleotide exchange. The mechanism responsible for this inhibition is one in which ADP-ribosylated Rap binds inefficiently to C3G, relative to wild type Rap. This identifies a second member of the Ras GTPase subfamily that can be ADP ribosylated by ExoS and indicates that ExoS can inhibit both Ras and Rap signaling pathways in eukaryotic cells.
Microbiology and Molecular Genetics, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, Wisconsin 53226, USA.
M J
MJ
Riese
A
A
Wittinghofer
J T
JT
Barbieri
D036002:ADP Ribose Transferases; D000246:Adenosine Diphosphate Ribose / Q000378:metabolism*; D001120:Arginine / Q000378:metabolism*; D001427:Bacterial Toxins; D020735:Guanine Nucleotide-Releasing Factor 2 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D006639:Histidine / Q000235:genetics; D000071677:Histidine Kinase; D010446:Peptide Fragments / Q000037:antagonists & inhibitors / Q000378:metabolism; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism*; D011550:Pseudomonas aeruginosa / Q000201:enzymology / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D020668:rap GTP-Binding Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism*
D001427:Bacterial Toxins; D020735:Guanine Nucleotide-Releasing Factor 2; D010446:Peptide Fragments; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D000246:Adenosine Diphosphate Ribose; D006639:Histidine; D001120:Arginine; D036002:ADP Ribose Transferases; D011065:Poly(ADP-ribose) Polymerases; C444820:exoenzyme S; D011494:Protein Kinases; D000071677:Histidine Kinase; D020668:rap GTP-Binding Proteins