Which of the following toxin acts by inhibiting protein synthesis?
Shiga toxin also known as verotoxin, was first identified in a major cause of dysentry called Shigella dysentriae. Shiga toxin contains an enzymatic domain and 5 binding domains which bind to globotriaosylceramide (Gb3), a glycosphingolipid on the surface of cells and the complex is internalized. The internalized shiga toxin hydrolyse the ribosomes, preventing fuher protein synthesis. Shiga toxin is composed of two distinct peptide subunits: The first located on the larger A subnit is an N-glycosidase that hydrolyzes adenine from specific sites of ribosomal RNA of the mammalian 60s ribosomal subunit, irreversibly inhibiting protein synthesis. The second is a binding site on the B subunit that recognizes glycolipids of target cell membranes (glycolipid Gb 3). Ref: Toxins and Hemostasis: From Bench to Bedside By R.Manjunatha Kiri, Page 642-643 ; Textbook of Pathology By V. Krishna, Page 178 ; Interaction of Pathogenic Bacteria with Host Cells By Virginia L. Clark, Volume 236, Page 67 ; Microorganisms in foods 5: Microbiological Specifications of Food Pathogens By International Commission on Microbiological Specifications for Food, Page127
Cholera toxin
LT of enterotoxigenic E.coli
Peusis toxin
Shiga toxin