6. As expected, mutation of D109, D111 and D306 completely disrupted catalysis. What role do these amino acids play that is shared by all DNA/RNA polymerases? (1 point) 7. Several of the tested residues were essential for catalytic activity, and their requirement was explained using the UTP-bound structure of the enzyme. For each residue named below, indicate the group that the amino acid interacts with and the type of interaction that is indicated by the structure. ( 2 points each) a) H315: b) K318: c) H166