Cholera is an infectious disease that spreads in countries without clean drinking water or adequate sewage disposal. The bacterium causing the disease was identified in 1884. How it causes disease was discovered almost 100 years later.
A toxin produced by the bacterium changes the G-proteins in cells lining the intestine. The G-proteins become "stuck" in the activated—or turned on—state. They can't turn themselves off as they do when normally regulated. The effect is that water is pumped continuously out of the cells into the intestines, causing dangerously severe diarrhea.
About the Diagram
Normally, both the receptor and the amplifier span the membrane. The G-protein sits on the inner surface of the membrane. This current view is a little different from Rodbell's original model. In a person with cholera, the G-protein is stuck in the "on" position-next to the AC molecule
