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Protein Folding 6: a tour of Hemoglobin
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Protein Folding
A Tour of Hemoglobin
The disease Sickle Cell Anemia is caused by a single amino acid substitution in the protein hemoglobin. Hemoglobin (Hb, for short) carries oxygen in red blood cells. Sickle cell hemoglobin molecules (HbS, for short), unlike Hb, stick to each other and form fibers that distort the shape of the blood cell, giving it a sickle shape. On this page you'll take a tour of normal Hb, and see the location where the single amino acid substitution occurs. On the next page, you'll see how HbS sticks together.
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<font size="3" face="Verdana, Arial, Helvetica, sans-serif">To <b>Rotate</b>
: Drag your mouse over the molecule<br>To <b>Zoom</b>: Hold down shift and
drag.<br>Press each button below to see different views of the molecule
(scroll down for more). </font>
<table border="0">
<tr>
<td valign="top" width="50">
1. <img usemap="#trace" src="button.gif">
</td>
<td valign="top">
<font color="green">Backbone</font><font size="3" face="Verdana, Arial, Helvetica, sans-serif"><br>This
button shows a trace of hemoglobin's carbon backbone. It's a line
connecting the amino acids in a chain. Hb is made up of four chains,
shown in different colors. The pink and blue ones, with 141 amino
acids each, are called the alpha chains. The green and yellow ones,
with 146 amino acids each, are called the beta chains.</font>
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2. <img usemap="#amino" src="button.gif">
</td>
<td>
<font color="green">Color by amino acid</font><font size="3" face="Verdana, Arial, Helvetica, sans-serif"><br>Each
segment of the chain representing one amino acid is shown in a
different color. </font>
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<tr>
<td valign="top">
3. <img usemap="#heme" src="button.gif">
</td>
<td>
<font color="green">Show hemes</font><font size="3" face="Verdana, Arial, Helvetica, sans-serif"><br>The
heme is a group of atoms attached to the protein specially for
carrying oxygen (it is not made up of amino acids). Here, each atom
is shown as a ball. The orange iron atom at the center of each heme
is where an oxygen molecule can attach to be carried by Hb. </font>
</td>
</tr>
<tr>
<td valign="top">
4. <img usemap="#cpk" src="button.gif">
</td>
<td>
<font color="green">Show all atoms</font><font size="3" face="Verdana, Arial, Helvetica, sans-serif"><br>Here
every atom in Hb is shown as a ball. This lets you see the shape of
its outer surface (what it "looks like" to other molecules). </font>
</td>
</tr>
<tr>
<td valign="top">
5. <img usemap="#glu6" src="button.gif">
</td>
<td>
<font color="green">Show Beta 6 Glutamic acid</font><font size="3" face="Verdana, Arial, Helvetica, sans-serif"><br>"Beta
6 Glutamic acid" stands for the sixth amino acid on Hb's beta
chains, which is a glutamic acid. It is shown here in red (you may
have to rotate to see it). This is where the substitution occurs in
the sickle cell mutant, HbS, which you will see on the next page. </font>
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<td width="350" align="center">
<img usemap="#reset" src="button.gif">
  <font color="green">Reset position</font>
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<body>
<font size="4" face="Verdana, Arial, Helvetica, sans-serif">How many amino
acids total make up one hemoglobin molecule? </font>
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<font size="4" face="Verdana, Arial, Helvetica, sans-serif">How many amino
acids in a sickle cell hemoglobin molecule are affected by the mutation? </font>
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