Enterotoxigenic E. coli toxin alters G_ through which mechanism?

Enterotoxigenic Escherichia coli (ETEC) is known for its ability to cause traveler's diarrhea, and it does so through the production of heat-labile toxin (LT) and heat-stable toxin (ST). The mechanism of action of the heat-labile toxin involves the ADP-ribosylation of the Gs alpha subunit, which is part of the stimulatory G protein associated with adenylate cyclase.

When the toxin ADP-ribosylates the Gs protein, it effectively locks the protein in its active form. This leads to continuous stimulation of adenylate cyclase, resulting in an excessive production of cyclic AMP (cAMP) within enterocytes (intestinal cells). The increase in cAMP causes a cascade of intracellular events that ultimately leads to the secretion of electrolytes and water into the intestinal lumen, which contributes to the watery diarrhea characteristic of ETEC infections.

Therefore, the correct answer highlights the mechanism by which ETEC effector proteins alter intracellular signaling pathways to disrupt normal water and electrolyte transport, leading to diarrhea.