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Ab initio solution and refinement of two high-potential iron protein structures at atomic resolution
E Parisini1, F Capozzi, P Lubini
1Institut für Anorganische Chemie, University of Göttingen, Tammannstrasse 4, D-37077, Göttingen, Germany.
Acta Crystallographica. Section D, Biological Crystallography
|October 26, 1999
Summary
Structural analysis of reduced high-potential iron protein (HiPIP) reveals key insights into its redox potential. The H42Q mutant
Area of Science:
- Biochemistry
- Structural Biology
- Crystallography
Background:
- High-potential iron proteins (HiPIPs) are crucial electron carriers in photosynthetic bacteria.
- Understanding HiPIP structure-function relationships is vital for elucidating electron transfer mechanisms.
Purpose of the Study:
- To determine the crystal structure of reduced HiPIP from Chromatium vinosum and its H42Q mutant.
- To investigate the structural basis for differences in redox potentials, particularly at lower pH.
Main Methods:
- X-ray crystallography was employed to solve the structures of wild-type and H42Q mutant HiPIP.
- Ab initio direct methods were used for structure solution at atomic resolution (0.93-1.20 Å).
- Restrained anisotropic refinement was performed for structural analysis.
Main Results:
- The crystal structures of reduced wild-type HiPIP and its H42Q mutant were determined in multiple crystal forms.
- The [Fe4S4](2+) clusters in wild-type and H42Q mutant HiPIP exhibit similar dimensions and tetragonal distortion.
- Structural differences are localized to the surface around the mutated residue, not within the cluster.
Conclusions:
- The redox potential differences in HiPIP, especially at lower pH, are primarily attributed to surface charge distribution.
- The study supports the hypothesis that surface interactions, rather than core cluster structure, modulate HiPIP's electrochemical properties.