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Biological activity of preformed cholera toxin‐ganglioside G M1 complex
Author(s) -
Fiani M. L.,
Macioce P.,
Gallina A.,
Tomasi M.
Publication year - 1984
Publication title -
journal of neuroscience research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.72
H-Index - 160
eISSN - 1097-4547
pISSN - 0360-4012
DOI - 10.1002/jnr.490120219
Subject(s) - cholera toxin , ganglioside , toxin , cholera , chemistry , biological activity , vibrio cholerae , microbiology and biotechnology , biology , biochemistry , in vitro , bacteria , genetics
Synthetic and natural amphiphiles, octyl glucoside, Nonidet P40, sodium dodecyl sulfate (SDS), gangliosides G M1 and G D1a , interact with cholera toxin (CLT) and with its active region (protomer A). The formation of CLT‐amphiphile complex leads to inhibition of ADP‐ribosyltransferase activity, a characteristic of protomer A elicited after thiol‐reagents treatment. In all cases the interaction produces the maximum inhibitory effect above the critical micellar concentration of amphiphiles, although monomers of SDS show inhibition activity as well. The gangliosides appear to be capable of altering bilayer organization of membrane, similar to synthetic detergents. When CLT‐ganglioside complexes were incubated with cell culture medium containing 10% fetal calf serum (FCS) the ADP‐ribosyltransferase activity was completely restored both in cholera toxin and in protomer A. Some protein of FCS, which is avid of gangliosides, seems to be responsible for reversibility of inhibition. The results indicate that the active site of protomer A may be located in a hydrophobic pocket of the toxin structure. Furthermore, CLT was bound to reconstituted Sendai virus envelopes (RSVEs), containing a small amount of G M1 . The RSVEs are made of membranous vesicles, capable of binding and fusing with host cell membrane. The incubation for 1 lhr of RSVE bearing CLT with Friend's erythroleukemic cells produced the stimulation of adenylate cyclase. This stimulation appears to be due to the translocation of the active subunit of CLT in the inner half of plasma membrane.