Introduction 
CLOSED 
Figure 24. A local reduction of the voltage differential may 
induce a sodium or potassium channel to change confor- 
mation from one allosteric form to another, thus opening 
the channel and leading to the free passage of ions. This 
change is presumably caused by key electrically charged 
amino acids in the channel protein, which shift their orien- 
tation in response to the changed electrical field. 
From Discovering Enzymes, by David Dressier and Hun- 
tington Potter, p. 233- Copyright® 1991 by David Dressier. 
Reprinted with permission by W.H. Freeman and Company. 
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