DNA Polymerase I: Difference between revisions

Line 41:

Here, Klentaq1's N-terminal, palm, fingers and thumb domains are yellow, magenta, green, and blue, respectively. The DNA is drawn in stick form colored according to atom type (template C cyan, primer C green, N blue, O red, and P orange).

In the structure on the left, the crystal had been soaked in a solution of dideoxy-CTP (ddCTP), which the enzyme had added to the 3' end of the primer chain (shown in space-filling form with C green), where it forms a base pair with the a template G. This terminates further primer extension due to the absence of a 3'-OH group at the 3' end of the primer strand. Nevertheless, a ddCTP (shown in space-filling form with C yellow) binds to the enzyme active site at the 3' end of the primer in a base pair with a template G as if it were preparing to add to the 3' end of the primer. In the structure on the right (2ktq), the ddCTP in the enzyme's active site had been depleted by soaking the crystal in a ddCTP-frree solution. Comparison of these two structures reveals that the structure on the left, the so-called closed conformation, differs from the that on the right, the so-called open conformation, by a hinge-like motion of the fingers domain away from the polymerase active site. The rest of the protein remains very nearly unchanged. This is more readily seen in the morph between the closed and open structures (in which, for technical reasons, the ddCTP in the closed conformation is not shown).

<scene name='Sandbox_dvoet/DNA_polymerase/Morphtest1/1'>morph test scene</scene>

Line 58:

A closeup of the active site region in the open conformation (''right'') reveals that the side chain of the conserved Tyr 671 (colored with C pink) is stacked on top of the template G that forms a base pair with the bound ddCTP, where it apparently participates in verifying that a Watson–Crick base pair has formed. In the closed conformation (''left''), Tyr 671, which is part of the fingers domain, has moved aside, presumably to permit the active site to form about the incoming dNTP (satisfy yourself that the Tyr 671 side chain is stacked on the template G in the open form but not in the closed form).

==References==

DNA Polymerase I: Difference between revisions

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@@ Line 41: / Line 41: @@
 <applet load='2ktq.pdb' size='450' frame='true' align='right' caption='Klentaq1–Open conformation' scene= 'Sandbox_dvoet/DNA_polymerase/Klentaq1-open_conformation/2'/>
-       Here, Klentaq1's N-terminal, palm, fingers and thumb domains are yellow, magenta, green, and blue, respectively. The DNA is drawn in stick form colored according to atom type (template C cyan, primer C green, N blue, O red, and P orange).
+Here, Klentaq1's N-terminal, palm, fingers and thumb domains are yellow, magenta, green, and blue, respectively. The DNA is drawn in stick form colored according to atom type (template C cyan, primer C green, N blue, O red, and P orange).
-      In the structure on the left, the crystal had been soaked in a solution of dideoxy-CTP (ddCTP), which the enzyme had added to the 3' end of the primer chain (shown in space-filling form with C green), where it forms a base pair with the a template G. This terminates further primer extension due to the absence of a 3'-OH group at the 3' end of the primer strand. Nevertheless, a ddCTP (shown in space-filling form with C yellow) binds to the enzyme active site at the 3' end of the primer in a base pair with a template G as if it were preparing to add to the 3' end of the primer. In the structure on the right (2ktq), the ddCTP in the enzyme's active site had been depleted by soaking the crystal in a ddCTP-frree solution. Comparison of these two structures reveals that the structure on the left, the so-called closed conformation, differs from the that on the right, the so-called open conformation, by a hinge-like motion of the fingers domain away from the polymerase active site. The rest of the protein remains very nearly unchanged. This is more readily seen in the morph between the closed and open structures (in which, for technical reasons, the ddCTP in the closed conformation is not shown).
+In the structure on the left, the crystal had been soaked in a solution of dideoxy-CTP (ddCTP), which the enzyme had added to the 3' end of the primer chain (shown in space-filling form with C green), where it forms a base pair with the a template G. This terminates further primer extension due to the absence of a 3'-OH group at the 3' end of the primer strand. Nevertheless, a ddCTP (shown in space-filling form with C yellow) binds to the enzyme active site at the 3' end of the primer in a base pair with a template G as if it were preparing to add to the 3' end of the primer. In the structure on the right (2ktq), the ddCTP in the enzyme's active site had been depleted by soaking the crystal in a ddCTP-frree solution. Comparison of these two structures reveals that the structure on the left, the so-called closed conformation, differs from the that on the right, the so-called open conformation, by a hinge-like motion of the fingers domain away from the polymerase active site. The rest of the protein remains very nearly unchanged. This is more readily seen in the morph between the closed and open structures (in which, for technical reasons, the ddCTP in the closed conformation is not shown).
 <scene name='Sandbox_dvoet/DNA_polymerase/Morphtest1/1'>morph test scene</scene>
@@ Line 58: / Line 58: @@
 <applet load='2ktq.pdb' size='450' frame='true' align='right' caption='Klentaq1–Open closeup' scene= 'Sandbox_dvoet/DNA_polymerase/Klentaq1-open_closeup/6'/>
-      A closeup of the active site region in the open conformation (''right'') reveals that the side chain of the conserved Tyr 671 (colored with C pink) is stacked on top of the template G that forms a base pair with the bound ddCTP, where it apparently participates in verifying that a Watson–Crick base pair has formed. In the closed conformation (''left''), Tyr 671, which is part of the fingers domain, has moved aside, presumably to permit the active site to form about the incoming dNTP (satisfy yourself that the Tyr 671 side chain is stacked on the template G in the open form but not in the closed form).
+A closeup of the active site region in the open conformation (''right'') reveals that the side chain of the conserved Tyr 671 (colored with C pink) is stacked on top of the template G that forms a base pair with the bound ddCTP, where it apparently participates in verifying that a Watson–Crick base pair has formed. In the closed conformation (''left''), Tyr 671, which is part of the fingers domain, has moved aside, presumably to permit the active site to form about the incoming dNTP (satisfy yourself that the Tyr 671 side chain is stacked on the template G in the open form but not in the closed form).
 ==References==
 <references/>