Calculate the concentration of lac repressor, assuming that one molecule is present per cell. Assume that each E. coli cell has a volume of 10-¹² cm³ . Would you expect the single molecule to be free or bound to DNA?

You plan to synthesize a peptide to be used as a vaccine to treat melanoma, a particularly aggressive form of skin cancer. Normally, gp100, a protein on the surface of melanocytes, activates cell growth when it is bound by its ligand. Activation of the growth pathway depends on the presence of threonine in the ligand. The effective peptide vaccine will mimic the natural ligand, but won’t cause cell growth and division. Below is the sequence of the natural ligand:   LDMKTAG   In order to ensure your newly designed peptide vaccine does not cause cell growth upon binding, you must substitute the Threonine residue at position 5. What amino acid would you replace it with, bearing in mind that the peptide should still be similar enough to bind to the gp100 protein in the surface of melanocytes. Explain your choice. Your vaccine will be administered as a topical cream, and you require your peptide to have an overall neutral charge in order to be functional. At what pH should you formulate…

Imagine that you created a cell that over-expresses a truncated version of its extrinsic pathway initiator caspase. This protein contains the caspase's DED, but none of the caspase's protease domains. This truncated version is present as an extra copy in addition to the WT copy. In 1-2 sentences, explain what the outcome would be on extrinsic apoptosis (i.e. would it be a positive/negative regulator/have no effect) and why.

Consider the mechanism of the enzyme RNase:   What would happen to the Km (i.e., would it increase, decrease, or stay the same) if the his12 was mutated to a lysine? Explain.   What would happen to the Kcat (i.e., would it increase, decrease, or stay the same) if the his12 was mutated to a valine? Explain.