Structure of E. coli DnaC helicase loader: Difference between revisions

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Eric Martz, David Canner, Michal Harel, Alexander Berchansky, Joel L. Sussman

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 <applet load='2chg9-63_aligned_with_dnac_model.pdb' size='400' frame='true' align='right' caption='Structural alignment.' scene='User:Eric_Martz/Sandbox_6/2qgz_3ec2_aligned_pdb/1'/>
-When the [[PDB]] is searched with the DnaC sequence, the best match (December, 208) is 23% sequence identity with 183 amino acids in the DnaC helicase loader of ''Aquifex aeolicus'', [[3ec2]] and [[3ecc]]. In order to find whether these structures have the same fold as the template ([[2qgz]] with 19% sequence identity to ''E. coli'' DnaC) used for the homology model, <font color="#3030ff">'''2qgz'''</font> was structurally aligned (<scene name='User:Eric_Martz/Sandbox_6/2qgz_3ec2_aligned_pdb/1'>restore initial alignment scene</scene>) with <font color="#ff0000">'''3ec2'''</font><ref>The structural alignment of 2qgz with 3ec2 was performed with the ''Magic Fit'' function of DeepView version 3.6beta2. 2qgz 115-259 aligned with 3ec2 42-185 (3 gaps in 3ec2's alignment: 128-9, 134-5, 155-9). 135 alpha carbons were aligned with RMS 2.76 Å. The structural alignment was performed without reference to sequence alignment. The sequence identity between 2qgz and 3ec2 is 28% over the 185 amino acid length of the shorter, 3ec2.</ref>. The similarity of folds lends considerable confidence to the homology model of ''E. coli'' DnaC.
+When the [[PDB]] is searched with the DnaC sequence, the best match (December, 208) is 23% sequence identity with 183 amino acids in the DnaC helicase loader of ''Aquifex aeolicus'', [[3ec2]] and [[3ecc]]. In order to find whether these structures have the same fold as the template ([[2qgz]] with 19% sequence identity to ''E. coli'' DnaC) used for the homology model, <font color="#3030ff">'''2qgz'''</font> was structurally aligned (<scene name='User:Eric_Martz/Sandbox_6/2qgz_3ec2_aligned_pdb/1'>restore initial alignment scene</scene>) with <font color="#ff0000">'''3ec2'''</font><ref>The structural alignment of 2qgz with 3ec2 was performed with the ''Magic Fit'' function of DeepView version 3.6beta2. 2qgz 115-259 aligned with 3ec2 42-185 (3 gaps in 3ec2's alignment: 128-9, 134-5, 155-9). 135 alpha carbons were aligned with RMS 2.76 Å. The sequence identity between 2qgz and 3ec2 is 28% over the 185 amino acid length of the shorter, 3ec2. ''Magic Fit'' is a sequence-alignment-guided structural alignment (see [[Structural_alignment_tools#DeepView_.3D_Swiss-PDBViewer|Structural alignment tools]]).</ref>. The similarity of folds lends considerable confidence to the homology model of ''E. coli'' DnaC.
 The second best sequence-identity hit in the PDB is 39% identity with 54 amino acids (positions 9-63 of chain A) of replication factor C ([[2chg]]), which align with 72-124 of DnaC. When the above homology model of DnaC (made with template 2QGZ) is <scene name='User:Eric_Martz/Sandbox_4/2chg9-63_aligned_with_dnac_mod/1'>structurally aligned</scene> with residues 9-63 of 2CHG<ref>Structural alignment done with DeepView 3.6b3 using Magic Fit of carbon alphas.</ref>, 43 alpha carbons (out of 54) aligned with RMS deviation 2.3 &Aring;. <font color="#ff0000">'''Residues 21-63 of 2CHG'''</font> aligned with <font color="#3030ff">'''residues 80-124 of the DnaC homology model'''</font>. (Non-aligned portions are pastel.) This result adds firther confidence to this region of the homology model, since the structural alignment of 2CHG:A21-63 occurred in the same range as the sequence alignment (which was 72-124 in DnaC).