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Toxins 2017, 9(4), 133; doi:10.3390/toxins9040133

Differences in Ribosome Binding and Sarcin/Ricin Loop Depurination by Shiga and Ricin Holotoxins

Department of Plant Biology, Rutgers, The State University of New Jersey, New Brunswick, NJ 08901, USA
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Academic Editors: Julien Barbier and Daniel Gillet
Received: 3 January 2017 / Revised: 28 March 2017 / Accepted: 5 April 2017 / Published: 11 April 2017
(This article belongs to the Special Issue Ribosome Inactivating Toxins)
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Abstract

Both ricin and Shiga holotoxins display no ribosomal activity in their native forms and need to be activated to inhibit translation in a cell-free translation inhibition assay. This is because the ribosome binding site of the ricin A chain (RTA) is blocked by the B subunit in ricin holotoxin. However, it is not clear why Shiga toxin 1 (Stx1) or Shiga toxin 2 (Stx2) holotoxin is not active in a cell-free system. Here, we compare the ribosome binding and depurination activity of Stx1 and Stx2 holotoxins with the A1 subunits of Stx1 and Stx2 using either the ribosome or a 10-mer RNA mimic of the sarcin/ricin loop as substrates. Our results demonstrate that the active sites of Stx1 and Stx2 holotoxins are blocked by the A2 chain and the B subunit, while the ribosome binding sites are exposed to the solvent. Unlike ricin, which is enzymatically active, but cannot interact with the ribosome, Stx1 and Stx2 holotoxins are enzymatically inactive but can interact with the ribosome. View Full-Text
Keywords: Shiga toxin 1; Shiga toxin 2; Stx1; Stx2; ricin; ribosome binding; depurination activity Shiga toxin 1; Shiga toxin 2; Stx1; Stx2; ricin; ribosome binding; depurination activity
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

Li, X.-P.; Tumer, N.E. Differences in Ribosome Binding and Sarcin/Ricin Loop Depurination by Shiga and Ricin Holotoxins. Toxins 2017, 9, 133.

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