Gating mechanisms other channels

The S. lividans K+ channel is not voltage gated. Voltage-gating mechanisms must be learned from study of other channels The voltage-dependent K+ channels from the rat have an a4P4 composition. The a and (3 subunits coassemble in the endoplasmic reticulum and remain as a permanent complex,3703 After insertion into the plasma membrane the a subunits form a channel as in Fig. 8-21. However, an additional intracellular domain of... 

In contrast to the structure of the K channel, the Cl" channel maintains a large cavity but the ion is surrounded by the positive amino ends (-NH3 ) of peptide chains. The pore channel/filter places amide nitrogen atoms (-CO-NH-) rather than carbonyl oxygen atoms in contact with Cl". The result is to create a low-energy pathway for an anion rather than for a cation through the Cl" membrane channel protein. MacKinnon s group and others are currently involved in studies of the structure and function of the gating mechanism that opens and closes the channel at the intracellular end. 

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