Some disease-causing microbes attack the body by turning on or off specific signal transduction pathways. In the disease cholera, the bacterium Vibrio cholerae causes massive diarrhea by interfering with such a pathway. A toxin from this bacterium enters intestinal cells and chemically modifies G proteins. Once modified, the G proteins can no longer cleave GTP into GDP. What would you expect to see within the intestinal cells of a person with cholera?
The G protein subunits do not separate from each other.
The G proteins remain activated and continually activate adenylyl cyclase.
The G proteins cannot become activated and cannot activate adenylyl cyclase.
The receptor in the membrane is continually activated.
