J. Biol. Chem., Vol. 262, Issue 19, 8966-8974, Jul, 1987
The interaction between the presynaptic phospholipase neurotoxins beta- bungarotoxin and crotoxin and mixed detergent-phosphatidylcholine micelles. A comparison with non-neurotoxic snake venom phospholipases A2
F Radvanyi, B Saliou, C Bon and PN Strong
Certain phospholipase A2 enzymes (E.C.3.1.1.4) selectively inhibit
neurotransmitter release from cholinergic nerve terminals. Both specific
acceptor proteins and the physical state of nerve terminal phospholipids
have been implicated in studies of the mechanism of phospholipase
neurotoxin action. Here we have examined the effects of charge on a
micellar phospholipid substrate by comparing the enzyme activity and
binding of two neurotoxic phospholipases (beta- bungarotoxin and crotoxin)
with other non-neurotoxic phospholipases. This has been achieved by
altering either the phospholipid or the ionic charge of the detergent in
the mixed phospholipid micelle. The neurotoxic phospholipases were only
active on negatively charged micelles, whereas the non-neurotoxic enzymes
were equally active in hydrolyzing neutral micelles. This distinction was
also reflected in binding studies; the non-neurotoxic phospholipases bound
to both types of substrate, whereas beta-bungarotoxin and crotoxin
selectively bound to negatively charged micellar structures. These
experiments suggest that, in addition to the existence of any specific
acceptor proteins, neurotoxin binding is also governed by the charge on the
lipid phase of the nerve terminal membrane.
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