Abstract
ADP-ribosylation is a reversible post-translational modification defined by adding ADP-ribose moieties from NAD + to the target. As bacterial toxins, cholera toxin ADP-ribosylates a specific arginine in the Gsα of heteromeric G-proteins, and diphtheria toxin ADP-ribosylates the eukaryotic elongation factor 2 (eEF2). Later, the ADP-ribosylating enzymes in cholera toxin and diphtheria toxin were named ARTC family and ARTD family, respectively, because there is each specific motives characterized ADP-ribosylating enzymes in cholera toxin and diphtheria toxin. We have studied functional studies based on the ARTC crystal structures. We especially revealed the complex structure of Ia-actin and C3-RhoA and the critical recognition mechanism of Arg and Asn ADP-ribosylation. Next, we revealed the ScARP structure, which participates in ADP-ribosylation from GDP. From these studies, we have concluded that although there are various substrates for ADP-ribosylating enzymes, there is a common substrate recognition mechanism regardless of protein and DNA for ADP-ribosylation. In addition, we have studied the protein translocation mechanism in binary toxins, such as C.perfringens iota toxin and C.difficile CDT. Using cryo-EM, we have revealed the binary toxin complex structure and the first unfolding structure of Ia and CDTa in these pore complexes.
