The A chain is shown in green and this is the enzymatic. It's the catalytic A chain that will cause its effect once it gets into the cell, as we'll see in just a moment. And these five binding b chains basically create this cyclical structure that ultimately is used to actually bind into a special region of the membrane of the intestinal epithelial cells. So once inside the loom of the small intestine, the cholera secretes, the cholera toxin we call chlorogen. This is a protein that consists of two types of chains, the A chains and the B chains. And they combine to form a hexameric structure as shown in this particular case.