Biochemistry 441 Bill Parson Homework set #5 1. The active form of pyruvate carboxylase is a tetramer of a protein with multiple domains. One domain of each monomeric unit contains a covalently bound molecule of biotin, which picks up CO 2 at a catalytic site in a biotin carboxylase (BC) domain and transfers the carboxyl group to pyruvate at a catalytic site in a carboxyl transferase (CT) domain. Assuming that you can dissociate the tetramer into the monomeric units and then reassemble it, how could you use site-directed mutations to find out whether the biotin bound to a given monomer serves the BC and CT domains of the same monomer or of different monomers? 2. The ACP domain of the fatty acid synthase must interact sequentially with five other catalytic domains of the protein during each turn of the cycle. What does this imply about the thermodynamics of its interactions with any given domain? 3.
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