Form Follows Function

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Form Follows Function

• What is the secret of Hb?

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What does the structure tell us?

• 4 globular protein chains
• Each protects a heme porphyrin
• Deoxy- and oxy-Hb are different shapes
• 1938 deoxy-Hb crystal exposed to air and shatters
• Fe in deoxy-Hb has 5 sites occupies
• 4 from porphyrin and 1 from Histidine (aa)
• Fe in oxy-Hb also has O2 in 6th site
• Hb is allosteric and exhibits cooperativity
• Changes shape as part of function

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Hbs big secret
Movement of proximal histidine distorts overall
structure
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HbF is a2g2 not a2b2