TitleThe role of the ribosomal stalk in the activity of ricin, Shiga-like toxin 1 and Shiga-like toxin 2 in Saccharomyces cerevisiae
NameChiou, Jiachi (author), Tumer, Nilgun E. (chair), Carman, George M. (internal member), Quadro, Loredana (internal member), Cohick, Wendie S. (outside member), Rutgers University, Graduate School - New Brunswick,
DescriptionRicin, Shiga-like toxin 1 (Stx1) and Shiga-like toxin 2 (Stx2) are ribosome inactivating proteins (RIPs) that catalytically remove an adenine residue from the highly conserved α-sarcin/ricin loop (SRL) in the large ribosomal subunit, inhibiting the translocation step of protein synthesis. Although all RIPs act on the same substrate, they differ in the ribosome specificity among different kingdoms. Ricin is only active towards the eukaryotic ribosomes, while Stx1 and Stx2 are active towards both prokaryotic and eukaryotic ribosomes. Infection with E. coli O157:H7 containing Stx2 is more likely to lead to hemolytic uremic syndrome (HUS) and progress to more severe disease than infection with E. coli O157:H7 containing Stx1. Accumulating evidence indicates that interaction of RIPs with different ribosomal proteins may be responsible for the ribosome specificity. By expressing the enzymatic A subunits of ricin, Stx1 and Stx2 in Saccharomyces cerevisiae, this study presents evidence that the ribosomal stalk is the docking site for ricin, Stx1 and Stx2, but not PAP. The results suggest that the P proteins of the ribosomal stalk recruit the RIPs to the ribosome to build a toxin pool near the SRL, facilitating depurination of the SRL. Stx2 depurinates ribosomes more efficiently than Stx1 regardless of the defects in the ribosomal stalk both in vitro and in vivo. Addition of purified P1α/P2β proteins has the most impact on the ribosome depurination by Stx1 than Stx2 and RTA. These results suggest that Stx1 is more dependent on the ribosomal stalk than Stx2. A model is proposed to describe the interaction between Stx1A and the ribosomal stalk. The ribosome-bound and the cytoplasmic pool of stalk P proteins play important roles in the depurination of the SRL, ribosome binding and cytotoxicity of the three different toxins. The cytoplasmic pool of P proteins and stalk conformation affect each toxin differently and these differences contribute to their relative cytotoxicity.
NoteIncludes bibliographical references
Noteby Jiachi Chiou
CollectionGraduate School - New Brunswick Electronic Theses and Dissertations
Organization NameRutgers, The State University of New Jersey
RightsThe author owns the copyright to this work.