Self-inhibiting N-glycosidase activity of shigella toxin
Polesskaia, A.N.; Garred, O.; Olsnes, S.; Kozlov, I.V.
Molekuliarnaia Biologiia 31(3): 528-535
1997
ISSN/ISBN: 0026-8984 PMID: 9297098 Document Number: 477838
Shigella toxin belongs to a broad family of bacterial toxins inhibiting protein synthesis in eukaryotic cells. Shigella toxin molecule is a hexamer formed by one A-subunit exhibiting specific N-glycosidase activity with respect to 28S ribosomal RNA and five B-subunits. X-ray data make it possible to assume that the enzymatically active center of the toxin is partially blocked by the C-terminal portion of A-subunit polypeptide chain. Site-directed mutagenesis and chemical protein modification were used to show that the disengagement of interaction between the active center of Shigella toxin and A-subunit polypeptide chain portion resulted in a 50-times increase in N-glycosidase activity of Shigella toxin in a cell-free system. Pathways of interaction of polypeptide chains were considered the basis of autoinhibition mechanism. Shigella toxin is produced by Shigella dysenteriae.