The non - phospholipase A 2 subunit of - bungarotoxin plays an important role in the phospholipase A 2 - independent neurotoxic effect : characterization of three isotoxins with a common phospholipase A 2 subunit

Three isotoxins (SP I-III) of the ,-bungarotoxin family were purified to homogeneity via a series of isolation procedures including a final step of h.p.l.c. on an SP column washed with a linear gradient of 0.2-0.6 M sodium acetate at pH 7.4. Their proportions varied greatly with the batch ofvenom. Each isotoxin was demonstrated by SDS/PAGE to contain a phospholipase A2 subunit and a non-phospholipase A2 subunit. The three proteins were reductively alkylated with 4-vinylpyridine and the alkylated derivatives of the two subunits of each isotoxin were separated. N-Terminal sequence analysis of the alkylated derivatives revealed that the three isotoxins probably share a common phospholipase A2 subunit but differ in their non-phospholipase A2 subunits. The non-phospholipase A2 subunits of SP II and SP III were identical with those of f32and Al-toxin respectively, except that there was an additional valine inserted between