Homework #33 CHEM 404 Assigned May 7, 2021 Due May 10, 2021 1

Homework #33 CHEM 404 Assigned May 7, 2021 Due May 10, 2021 1. In “protein #1,” a rather small protein, there are two Zn2+ ions bound to four cysteine amino acids each in roughly tetrahedral geometry. In another protein, “protein #2,” a water-soluble protein, there is a single Fe2+ ion bound to four cysteine amino acids in roughly tetrahedral geometry. In “protein #3,” there is an iron bound by a porphyrin with a histidine binding to the metal on one side of the porphyrin, and a cysteine amino acid on the opposite side. The Fe porphyrin is near one side protein #3, a fairly large protein which has limited solubility. What roles are the transition metals likely to play in the three proteins? Please explain your reasoning for each answer. 2. In the lecture, I covered several enzymes that made zinc-bound oxygens more reactive, for example making bound waters more easily deprotonated to become OH– ligands. Turning H2O into OH–, however, is something that a lot of transition metals can do. Discuss at least two reasons why Zn2+ ions might be more advantageous to use instead of, for example, Fe2+.