Inverse control of Rab proteins by <i>Yersinia</i> ADP-ribosyltransferase and glycosyltransferase related to clostridial glucosylating toxins.

Abstract

We identified a glucosyltransferase (YGT) and an ADP-ribosyltransferase (YART) in <i>Yersinia mollaretii</i>, highly related to glucosylating toxins from <i>Clostridium difficile</i>, the cause of antibiotics-associated enterocolitis. Both <i>Yersinia</i> toxins consist of an amino-terminal enzyme domain, an autoprotease domain activated by inositol hexakisphosphate, and a carboxyl-terminal translocation domain. YGT <i>N</i>-acetylglucosaminylates Rab5 and Rab31 at Thr⁵² and Thr³⁶, respectively, thereby inactivating the Rab proteins. YART ADP-ribosylates Rab5 and Rab31 at Gln⁷⁹ and Gln⁶⁴, respectively. This activates Rab proteins by inhibiting GTP hydrolysis. We determined the crystal structure of the glycosyltransferase domain of YGT (YGT^G) in the presence and absence of UDP at 1.9- and 3.4-Å resolution, respectively. Thereby, we identified a previously unknown potassium ion-binding site, which explains potassium ion-dependent enhanced glycosyltransferase activity in clostridial and related toxins. Our findings exhibit a novel type of inverse regulation of Rab proteins by toxins and provide new insights into the structure-function relationship of glycosyltransferase toxins.