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Redox-dependent structural differences in putidaredoxin derived from homologous structure refinement via residual
Nitin U Jain1, Elina Tjioe, Alon Savidor
1Biochemistry, Cellular and Molecular Biology Department, University of Tennessee, Knoxville, Tennessee 37996-0840, USA. njain@utk.edu
Biochemistry
|June 22, 2005
Summary
Structural studies of putidaredoxin (Pdx) reveal redox-dependent differences in its iron cluster. These changes influence its interaction with cytochrome P450(cam), impacting biological electron transfer.
Area of Science:
- Biochemistry
- Structural Biology
- Biophysics
Background:
- Putidaredoxin (Pdx) is a [2Fe-2S] ferredoxin crucial for camphor hydroxylation by Pseudomonas putida.
- Pdx facilitates biological electron transfer to cytochrome P450(cam) (CYP101).
- Previous studies indicated redox-dependent variations in Pdx binding affinities, NMR spectra, and dynamics.
Purpose of the Study:
- To refine and compare the structures of oxidized and reduced Pdx.
- To identify specific structural differences correlated with redox state.
- To understand how these structural changes affect Pdx function.
Main Methods:
- Utilized a hybrid approach for structure refinement of Pdx.
- Incorporated paramagnetic distance restraints and NMR residual dipolar couplings (RDCs).
- Calculated structures for both oxidized and reduced Pdx states.
Main Results:
- Improved structural model for oxidized Pdx, aligning with X-ray crystallography data.
- Observed better-defined secondary structures and metal-binding loop conformations.
- Identified localized structural differences in reduced Pdx, particularly in the C-terminal domain and near the metal-binding loop.
Conclusions:
- Redox-dependent structural changes in Pdx are primarily localized.
- These differences involve key residues like Trp 106 and the metal-binding loop region.
- Structural variations correlate with previously observed dynamic changes and may explain altered binding and electron transfer properties.