W04-mtkey25 - Name _Both versions Wed Mar 25_ 21. The...

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21. The figures represent the environment around heme in β -globin. Identify which represents T-state and which is R-state (1 mark) What component of the opposite α -globin interacts with His HC3? State: __ R ___ State: _ T ____ ___ Lys (1) C5 _(1)_____________ (2 marks) Briefly explain how the presence of His HC3 is responsible for low O 2 affinity. (3 marks) In T-state, His HC3 can form an ion pair with Asp FG1 on the same b -globin Tension from this ion pair pulls Helix F away from heme His F8 pulls Fe 2+ out of the heme plane, making it less accessible to O 2 in the ligand 6 position How will an increase in pH help shift to R-state? (3 marks) Higher pH causes His HC3 side chain to deprotonate and lose its charge This breaks the ion pair with Asp FG1 Helix F and the Fe 2+ relax to their natural state When O 2 binds in one or two sites of hemoglobin, how does this cause the vacant globin subunits to switch to R-state at the same time (3 marks) Each O 2 that binds applies an opposing force on Fe 2+ ; and each O2 increases the probability of switch to R state When the switch occurs, the whole hemoglobin molecule changes state in all its subunits simultaneously (MWC model) Hemoglobin switches state by a single global change, rotation of a1b1 a1b1 relative to a2b2 a2b2 , which changes the interactions between neighbouring globins Name ____Both versions Wed Mar 25______ Student number ____________________
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22. Explain the metabolic logic suggested by each of the following allosteric regulators:
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This note was uploaded on 04/08/2010 for the course BIOC 3560 taught by Professor Dawson during the Spring '10 term at University of Guelph.

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W04-mtkey25 - Name _Both versions Wed Mar 25_ 21. The...

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