This element is found in rubredoxin proteins, where it (10[1])is coordinated by four cysteine residues. Proteins that catalyze redox reactions often have clusters of this element and sulfur. An ion (10[1])of this element (10[2])is found in the active site of an enzyme (-5[1])that degrades hydrogen peroxide, catalase. A protein that contains an ion of this element transitions from a T to R state upon oxygen binding. (10[1])That protein is also compromised (10[1])in individuals with (10[1])thalassemia, and the heme group is responsible for binding an ion of this element. (10[1])A deficiency of this element in the body (10[1])results in anemia. For 10 points, name this metallic element whose ion gives blood its red color. (10[1])■END■