The disease cholera results from infection of the epithelial cells of the gut by the phage Vibrio cholerae. The phage-infected cells produce new proteins, cholera toxin A and cholera toxin B, that are secreted into the gut. Cholera toxin B assembles into multisubunit complexes in the membranes of gut eptitheial cells and permits the toxic cholera toxin A to enter these cells, causing an ion imbalance and massive, watery diarrhea which permits the phage to spread to a new host. The structural assembly of cholera toxin B into multisubunit complexes is an example of: a. primary structure
b. secondary structure
c. tertiary stucture
d. quaternary structure
e. All of the Above