Hemoglobin: Difference between revisions

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Here we see a single <scene name='Hemoglobin/3hhb_chaina_rainbow/4'>α chain</scene> of hemoglobin, starting with an overview of the subunit. The 6 major and 2 short α-helices that make up the structure of a Hb subunit (the "globin fold") are <scene name='Hemoglobin/3hhb_chaina_heliceslabeled/4'>labeled A through H</scene>, which is the traditional naming scheme. For example, the proximal histidine (the tightest protein Fe ligand) is often called <scene name='~~Hemoglobin~~/~~3hhb_chaina_hisf9~~/5'>His F9</scene>, since it is residue 9 on helix F (it is residue 87 in the human α chain). The helices form an approximately-cylindrical bundle, with the heme and its central Fe atom bound in a <scene name='Hemoglobin/3hhb_chaina_efpocket/4'>hydrophobic pocket between the E and F helices</scene>.

Here we see a single <scene name='Hemoglobin/3hhb_chaina_rainbow/4'>α chain</scene> of hemoglobin, starting with an overview of the subunit. The 6 major and 2 short α-helices that make up the structure of a Hb subunit (the "globin fold") are <scene name='Hemoglobin/3hhb_chaina_heliceslabeled/4'>labeled A through H</scene>, which is the traditional naming scheme. For example, the proximal histidine (the tightest protein Fe ligand) is often called <scene name='32/32/Hisf9/1'>His F9</scene>, since it is residue 9 on helix F (it is residue 87 in the human α chain). The helices form an approximately-cylindrical bundle, with the heme and its central Fe atom bound in a <scene name='Hemoglobin/3hhb_chaina_efpocket/4'>hydrophobic pocket between the E and F helices</scene>.

<scene name='32/32/Cv/2'>In the present animation scene</scene> the oxy (in pink) and deoxy (in deepskyblue) α1 heme groups were superimposed on each other, to give a local comparison at this site, a closeup around the heme O2-binding site. The heme is quite domed in the deepskyblue T-state (deoxy) form, with the 5-coordinate, high-spin Fe (orange ball) out of the plane. In the pink R-state form a CO molecule is bound at the right (C in green,O in red); the Fe, now 6-coordinate low-spin, has moved into the heme plane, which has flattenened. The proximal His (at left) connects the Fe to helices on the proximal side, making the Fe position sensitive to changes in the globin structure and vice versa. Remember that this scene shows a subunit in the all-unliganded versus the all-liganded states of Hb; when oxygen binds to just one subunit, then its internal structure undergoes some but not all of these changes, depending on conditions. <jmol><jmolButton>

Hemoglobin: Difference between revisions

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 <!-- <applet load='3hhb' size='400' frame='true' align='right' caption='Human deoxyhemoglobin (PDB code [[3hhb]])'/> -->
-Here we see a single <scene name='Hemoglobin/3hhb_chaina_rainbow/4'>α chain</scene> of hemoglobin, starting with an overview of the subunit.  The 6 major and 2 short α-helices that make up the structure of a Hb subunit (the "globin fold") are <scene name='Hemoglobin/3hhb_chaina_heliceslabeled/4'>labeled A through H</scene>, which is the traditional naming scheme.  For example, the proximal histidine (the tightest protein Fe ligand) is often called <scene name='Hemoglobin/3hhb_chaina_hisf9/5'>His F9</scene>, since it is residue 9 on helix F (it is residue 87 in the human α chain).  The helices form an approximately-cylindrical bundle, with the heme and its central Fe atom bound in a <scene name='Hemoglobin/3hhb_chaina_efpocket/4'>hydrophobic pocket between the E and F helices</scene>.
+Here we see a single <scene name='Hemoglobin/3hhb_chaina_rainbow/4'>α chain</scene> of hemoglobin, starting with an overview of the subunit.  The 6 major and 2 short α-helices that make up the structure of a Hb subunit (the "globin fold") are <scene name='Hemoglobin/3hhb_chaina_heliceslabeled/4'>labeled A through H</scene>, which is the traditional naming scheme.  For example, the proximal histidine (the tightest protein Fe ligand) is often called <scene name='32/32/Hisf9/1'>His F9</scene>, since it is residue 9 on helix F (it is residue 87 in the human α chain).  The helices form an approximately-cylindrical bundle, with the heme and its central Fe atom bound in a <scene name='Hemoglobin/3hhb_chaina_efpocket/4'>hydrophobic pocket between the E and F helices</scene>.
 <scene name='32/32/Cv/2'>In the present animation scene</scene> the <span style="color:pink;background-color:black;font-weight:bold;">oxy (in pink)</span> and <span style="color:deepskyblue;background-color:black;font-weight:bold;">deoxy (in deepskyblue)</span> α1 heme groups were superimposed on each other, to give a local comparison at this site, a closeup around the heme O2-binding site.  The heme is quite domed in the <span style="color:deepskyblue;background-color:black;font-weight:bold;">deepskyblue T-state (deoxy) form</span>, with the 5-coordinate, high-spin <span style="color:orange;background-color:black;font-weight:bold;">Fe (orange ball)</span> out of the plane.  In the <span style="color:pink;background-color:black;font-weight:bold;">pink R-state form</span> a CO molecule is bound at the right <span style="color:lime;background-color:black;font-weight:bold;">(C in green</span>,<font color='red'><b>O in red</b></font>); the Fe, now 6-coordinate low-spin, has moved into the heme plane, which has flattenened.  The proximal His (at left) connects the Fe to helices on the proximal side, making the Fe position sensitive to changes in the globin structure and vice versa.  Remember that this scene shows a subunit in the all-unliganded versus the all-liganded states of Hb; when oxygen binds to just one subunit, then its internal structure undergoes some but not all of these changes, depending on conditions.   <jmol><jmolButton>