Gating machinery

No drastic change occurred in tail sodium current. When tetramethrin was added to the BTX-treated axon, a large and prolonged tail current characteristic of the tetramethrin modified sodium channel developed. Thus tetramethrin binds to a site different from the binding site of BTX which is located inside of the channel. This result is compatible with the hypothesis that the pyrethroid molecules bind to the channel gating machinery via the membrane lipid phase thereby altering the kinetics of channel gating. 

Ca channels consist of a multiple subunit protein complex with a central pore-forming ai subunit and several regulatory and/or auxiliary subunits, which include (3 subunits, y subunits, and the disulfide-linked subunit. The subunit contains the Ca " conductance pore, the essential gating machinery, the receptor sites for the most prominent pharmacological agents, and modulatory... 

Figure 6-42. Helical four fluted gate blower rotors/two lobes main rotor intermeshing. See Figure 6-44. By permission, Gardner-Denver Industrial Machinery-Cooper Industries.

The decisive element in exocytosis is the interaction between proteins known as SNAREs that are located on the vesicular membrane (v-SNAREs) and on the plasma membrane (t-SNAREs). In the resting state (1), the v-SNARE synaptobrevin is blocked by the vesicular protein synaptotagmin. When an action potential reaches the presynaptic membrane, voltage-gated Ca "" channels open (see p. 348). Ca "" flows in and triggers the machinery by conformational changes in proteins. Contact takes place between synaptobrevin and the t-SNARE synaptotaxin (2). Additional proteins known as SNAPs bind to the SNARE complex and allow fusion between the vesicle and the plasma membrane (3). The process is supported by the hydrolysis of GTP by the auxiliary protein Rab. 

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