2q6n
From Proteopedia
(New page: 200px<br /><applet load="2q6n" size="350" color="white" frame="true" align="right" spinBox="true" caption="2q6n, resolution 3.200Å" /> '''Structure of Cytoch...) |
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==Overview== | ==Overview== | ||
| - | The crystal structure of P450 2B4 bound with 1-(4-chlorophenyl)imidazole | + | The crystal structure of P450 2B4 bound with 1-(4-chlorophenyl)imidazole (1-CPI) has been determined to delineate the structural basis for the observed differences in binding affinity and thermodynamics relative to 4-(4-chlorophenyl)imidazole (4-CPI). Compared with the previously reported 4-CPI complex, there is a shift in the 1-CPI complex of the protein backbone in helices F and I, repositioning the side chains of Phe-206, Phe-297, and Glu-301, and leading to significant reshaping of the active site. Phe-206 and Phe-297 exchange positions, with Phe-206 becoming a ligand-contact residue, while Glu-301, rather than hydrogen bonding to the ligand, flips away from the active site and interacts with His-172. As a result the active site volume expands from 200 A3 in the 4-CPI complex to 280 A3 in the 1-CPI complex. Based on the two structures, it was predicted that a Phe-206-->Ala substitution would alter 1-CPI but not 4-CPI binding. Isothermal titration calorimetry experiments indicated that this substitution had no effect on the thermodynamic signature of 4-CPI binding to 2B4. In contrast, relative to wild-type 1-CPI binding to F206A showed significantly less favorable entropy but more favorable enthalpy. This result is consistent with loss of the aromatic side chain and possible ordering of water molecules, now able to interact with Glu-301 and exposed residues in the I-helix. Hence, thermodynamic measurements support the active site rearrangement observed in the crystal structure of the 1-CPI complex and illustrate the malleability of the active site with the fine-tuning of residue orientations and thermodynamic signatures. |
==About this Structure== | ==About this Structure== | ||
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[[Category: Single protein]] | [[Category: Single protein]] | ||
[[Category: Unspecific monooxygenase]] | [[Category: Unspecific monooxygenase]] | ||
| - | [[Category: Halpert, J | + | [[Category: Halpert, J R.]] |
[[Category: Kumar, S.]] | [[Category: Kumar, S.]] | ||
| - | [[Category: Muralidhara, B | + | [[Category: Muralidhara, B K.]] |
| - | [[Category: Stout, C | + | [[Category: Stout, C D.]] |
[[Category: Sun, L.]] | [[Category: Sun, L.]] | ||
| - | [[Category: White, M | + | [[Category: White, M A.]] |
[[Category: Zhao, Y.]] | [[Category: Zhao, Y.]] | ||
[[Category: 1CI]] | [[Category: 1CI]] | ||
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[[Category: p450]] | [[Category: p450]] | ||
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 18:36:34 2008'' |
Revision as of 16:36, 21 February 2008
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Structure of Cytochrome P450 2B4 with Bound 1-(4-cholorophenyl)imidazole
Overview
The crystal structure of P450 2B4 bound with 1-(4-chlorophenyl)imidazole (1-CPI) has been determined to delineate the structural basis for the observed differences in binding affinity and thermodynamics relative to 4-(4-chlorophenyl)imidazole (4-CPI). Compared with the previously reported 4-CPI complex, there is a shift in the 1-CPI complex of the protein backbone in helices F and I, repositioning the side chains of Phe-206, Phe-297, and Glu-301, and leading to significant reshaping of the active site. Phe-206 and Phe-297 exchange positions, with Phe-206 becoming a ligand-contact residue, while Glu-301, rather than hydrogen bonding to the ligand, flips away from the active site and interacts with His-172. As a result the active site volume expands from 200 A3 in the 4-CPI complex to 280 A3 in the 1-CPI complex. Based on the two structures, it was predicted that a Phe-206-->Ala substitution would alter 1-CPI but not 4-CPI binding. Isothermal titration calorimetry experiments indicated that this substitution had no effect on the thermodynamic signature of 4-CPI binding to 2B4. In contrast, relative to wild-type 1-CPI binding to F206A showed significantly less favorable entropy but more favorable enthalpy. This result is consistent with loss of the aromatic side chain and possible ordering of water molecules, now able to interact with Glu-301 and exposed residues in the I-helix. Hence, thermodynamic measurements support the active site rearrangement observed in the crystal structure of the 1-CPI complex and illustrate the malleability of the active site with the fine-tuning of residue orientations and thermodynamic signatures.
About this Structure
2Q6N is a Single protein structure of sequence from Oryctolagus cuniculus with and as ligands. Active as Unspecific monooxygenase, with EC number 1.14.14.1 Full crystallographic information is available from OCA.
Reference
Structural and thermodynamic consequences of 1-(4-chlorophenyl)imidazole binding to cytochrome P450 2B4., Zhao Y, Sun L, Muralidhara BK, Kumar S, White MA, Stout CD, Halpert JR, Biochemistry. 2007 Oct 16;46(41):11559-67. Epub 2007 Sep 22. PMID:17887776
Page seeded by OCA on Thu Feb 21 18:36:34 2008
Categories: Oryctolagus cuniculus | Single protein | Unspecific monooxygenase | Halpert, J R. | Kumar, S. | Muralidhara, B K. | Stout, C D. | Sun, L. | White, M A. | Zhao, Y. | 1CI | HEM | Cyp 2b4 | Cyp lm2 | Membrane protein | Monooxygenase | Oxidoreductase | P450
