Microorganisms and Disease
Cholera toxin is an A-B type toxin in which the B portions bind to a receptor on a host cell and the A portion enters the cell to cause

ADP ribosylation of guanylate cyclase that stimulates production of cGMP
ADP ribosylation of a G protein that locks it into an active form that stimulates adenylate cyclase to make cAMP
ADP ribosylation of adenylate cyclase that stops production of cAMP
cleavage of rRNA that results in disruption of ribosome function