Question

Ricin is one of the most powerful toxins known. The protein consists of two subunits: the A chain is an enzyme that inhibits translation and the B chain is a lectin that binds to carbohydrates on the cell surface. What is the most likely mechanism by which ricin enters the cell?

The A chain binds to clathrin.

The A chain stimulates autophagy.

The B chain interacts with SNAREs.

The protein enters through pore complexes in the plasma membrane.

The protein is internalized by endocytosis.

Answer 1

The B chain of ricin binds to sugars on the cell surface which facilitates the toxin's internalization into the cell through endocytosis. After entering, the toxin separates in the acidic vacuole environment, releasing the toxic A chain into the cytoplasm.

Step-by-step explanation:

Ricin is a powerful toxin composed of two subunits: the A chain and the B chain. The B chain of ricin binds to carbohydrates on the cell surface, while the A chain is responsible for its toxic effect by inhibiting protein translation within the cell. The most likely mechanism by which ricin enters the cell is that, following the binding of the B chain to cell surface receptors, the entire protein is internalized by endocytosis. Once inside the cell, the ricin molecule is found within a vacuole where it undergoes acidification, allowing for the separation and release of the A subunit into the cytoplasm to exert its toxic effects.