A protein's structure often plays an important role in its function. Describe how the shapes of the sonic hedgehog protein and the cell surface protein coded for by the patched gene work together to control normal cell division. How is this altered in a person with Basal Cell Nevus Syndrome or in a person that has been exposed to too much UV radiation?

Question

What will be an ideal response?

Answer 1

In a normal person, the patched gene codes for cell surface proteins that serve as receptors for the sonic hedgehog protein. The shapes of these two proteins are such that the proteins fit together like a lock and key. When the sonic hedgehog protein fits into a receptor protein, the signal is sent to tell the cell to start dividing. When the sonic hedgehog protein is not bound to the receptor, cell division ceases. In a person with BCNS or in a person who has been exposed to too much UV radiation, the patched gene is altered. The gene now codes for a protein with a slightly different shape. This new shape prevents the receptor from recognizing the sonic hedgehog protein so no binding occurs. In addition, the new shape mimics the shape of a bound receptor. Thus the message is sent to begin cell division, and the message never ceases.