In:
Biochemical Journal, Portland Press Ltd., Vol. 367, No. 3 ( 2002-11-01), p. 801-808
Abstract:
Clostridium perfringens type E iota toxin consists of two unlinked proteins designated as iota a (Ia; molecular mass47kDa), an ADP-ribosyltransferase and iota b (Ib; molecular mass81kDa) which binds to the cell surface and facilitates Ia entry into the cytosol. By Western-blot analysis, Ib incubated with Vero cells at 37°C generated a cell-associated, SDS-insoluble oligomer of Ib (molecular mass & gt;220kDa) within 15s, which was still evident 110min after washing cells. Ib oligomerization was temperature, but not pH, dependent and was facilitated by a cell-surface protein(s). Within 5min at 37°C, cell-bound Ib generated Na+/K+ permeable channels that were blocked by Ia. However, Ib-induced channels or oligomers were not formed at 4°C. Two monoclonal antibodies raised against Ib that recognize unique, neutralizing epitopes within residues 632—655 either inhibited Ib binding to cells and/or oligomerization, unlike a non-neutralizing monoclonal antibody that binds within Ib residues 28—66. The Ib protoxin (molecular mass98kDa), which does not facilitate iota cytotoxicity but binds to Vero cells, did not oligomerize or form ion-permeable channels on cells, and neither trypsin nor chymotrypsin treatment of cell-bound Ib protoxin induced large complex formation. The link between Ib oligomers and iota toxicity was also apparent with a resistant cell line (MRC-5), which bound to Ib with no evidence of oligomerization. Overall, these studies revealed that the biological activity of iota toxin is dependent on a long-lived, cell-associated Ib complex that rapidly forms ion-permeable channels in cell membranes. These results further reveal the similarities of C. perfringens iota toxin with other bacterial binary toxins produced by Bacillus anthracis and C. botulinum.
Type of Medium:
Online Resource
ISSN:
0264-6021
,
1470-8728
Language:
English
Publisher:
Portland Press Ltd.
Publication Date:
2002
detail.hit.zdb_id:
1473095-9
SSG:
12
Permalink