Figure 3.

Binding of [³⁵S]synaptotagmin I to GST fusion proteins containing intracellular sodium channel domains. GST fusion proteins (1 μM) containing cytoplasmic domains of αIIA sodium channel subunit, β1 and β2 subunits (A), and loop I-II of αSkM1 sodium channel (B) were immobilized on glutathione-agarose beads and were incubated at 4°C for 4–5 h with in vitro translated [³⁵S]methionine-labeled synaptotagmin I (SYT I); bound proteins were eluted in sample buffer and were analyzed on SDS/PAGE by autoradiography (A), or bound radioactivity was measured by scintillation counting (B) (mean ± SD, n = 3). The last lane of the autoradiogram contains 1 μl of [³⁵S]synaptotagmin I (Tr.).