Hemoglobin: Difference between revisions

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O2 binds in the same place as CO, with similar effects on the structure; however, for O2 the outer atom is angled rather than straight. The equilibrium between free and bound O2 is very rapid, with on and off rates that are sensitive to protein conformation. Both CO and NO dissociate from the Fe atom very slowly, so that these gases act as respiratory poisons. The α and β chains differ somewhat in their rates and relative affinities for O2 and other ligands, by virtue of heme-pocket differences, but the differences between affinities in the R vs T quaternary states are much larger.

Both α and β chains of Hb resemble [[myoglobin]] (the single-chain O2-binder in muscle), both in overall tertiary structure and in using an Fe atom centered in a heme group as the site where oxygen is reversibly bound. The heme is surrounded by a hydrophobic pocket, which is necessary in order for it to bind oxygen reversibly without undergoing oxidation or other undesirable reactions.

Hemoglobin: Difference between revisions

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 <kinemage align="left" width="420" height="300" file="HbAllo.kin" />
-O2 binds in the same place as CO, with similar effects on the structure;  however, for O2 the outer atom is angled rather than straight.  The equilibrium between free and bound O2 is very rapid, with on and off rates that are sensitive to protein conformation.  Both CO and NO dissociate from the Fe atom very slowly, so that these gases act as respiratory poisons.  The α and β chains differ somewhat in their rates and relative affinities for O2 and other ligands, by virtue of heme-pocket differences, but the differences between affinities in the R vs T quaternary states are much larger.
+O2 binds in the same place as CO, with similar effects on the structure; however, for O2 the outer atom is angled rather than straight.  The equilibrium between free and bound O2 is very rapid, with on and off rates that are sensitive to protein conformation.  Both CO and NO dissociate from the Fe atom very slowly, so that these gases act as respiratory poisons.  The α and β chains differ somewhat in their rates and relative affinities for O2 and other ligands, by virtue of heme-pocket differences, but the differences between affinities in the R vs T quaternary states are much larger.
 Both α and β chains of Hb resemble [[myoglobin]] (the single-chain O2-binder in muscle), both in overall tertiary structure and in using an Fe atom centered in a heme group as the site where oxygen is reversibly bound.  The heme is surrounded by a hydrophobic pocket, which is necessary in order for it to bind oxygen reversibly without undergoing oxidation or other undesirable reactions.