Monday's Molecule #202

The last Monday's Molecule was the pyrrolysine, 23rd amino acid. The winner was Michael Florea [Monday's Molecule #201].

Today's molecule is an enzyme. Homologous enzymes are found in all species. They play an essential role in metabolism. The green part binds the substrate and the subsequent reaction reduces a bound FAD prosthetic group (yellow). Electrons are then passed to an FAD molecule in the purple part in the orientation shown on the left. Notice that the yellow FAD molecules are close together. (The two purple parts on the left should be joined but the connection can't be resolved in the structure.) This electron transfer results in a shift in conformation to the conformation of the purple structure shown on the right. Note that the FAD molecule has shifted to a less exposed position. The purple protein then dissociates and carries electrons to an membrane-bound enzyme that transfers electrons to ubiquinol (QH₂). Name the green protein and the purple protein.

This week I'm trying a new format in order to avoid moderating comments. Email your answers to me at: Monday's Molecule #202. I'll hold off posting your answers for 24 hours. The first one with the correct answer wins. I will only post mostly correct answers to avoid embarrassment. The winner will be treated to a free lunch.

There could be two winners. If the first correct answer isn't from an undergraduate student then I'll select a second winner from those undergraduates who post the correct answer. You will need to identify yourself as an undergraduate in order to win. (Put "undergraduate" at the bottom of your email message.)

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Posted in: Biochemistry