Question

Describe in detail the shiga toxin. How does it reach the target within a cell ?

Answer 1

Shiga toxin is one of the most vigorous toxins found in bacteria. This toxin is a family of related toxin and has two major subgroup - Stx1 and Stx2. Stx1 is mostly found in Shigella dysenteriae 1 and few serogroups of E. coli. Stx2 the second type of strain is found in E. coli. Mode of action of Stx1 and Stx2 is same but is antigenically distinct.

These Stxs binds to Gb3 (glycosphingolipid). Gb3 is made up of lipid or a ceramide component and a trisaccharide. Mostly it has been found that mice and cell lines are deficient of Gb3 and so they are insensitive to these toxins. Sometimes these toxins binds to Gb4 (globotetraocylceramide) instead. But the bond between the toxin and Gb4 is weak. Cells which do not express Gb3 or Gb4 there these toxins enters the cells through macropinocytosis.