Question

A mutation within a yeast cell has left it with very slow growth. After running all of the proteins from this cell on an acrylamide gel you see that all of the cell’s proteins are present in normal proportions, but a Bradford assay tells you that the total amount of protein in the mutant yeast cell is significantly decreased. What could explain the reduction in global protein production within this yeast cell?

Propose a specific, testable hypothesis that could be one possible explanation to the following questions. Describe the knowledge and assumptions that lead to each hypothesis, clearly identifying each.

Answer 1

A mutation within the yeast cell has caused slow growth and significant decrease in the total amount of protein. However, the proportions of all of the cell's proteins remain the same. Therefore, the mutation has not affected the expression of any specific protein. Because the global protein production within the yeast cell has been affected, the mutation must have affected the translational machinery of the cell.

Assuming that the rate limiting step for protein production in yeast cells is the availability of free ribosomes, it can be hypothesized that the mutation prevents a balanced production of ribosome components such as the ribosomal RNA molecules or binding to ribosomal proteins.