Outer-Sphere Effects on Reduction Potentials of Copper Sites in Proteins: The Curious Case of High Potential Type 2 C112D/M121E Pseudomonas aeruginosa Azurin
Abstract
Redox and spectroscopic (electronic absorption, multifrequency electron paramagnetic resonance (EPR), and X-ray absorption) properties together with X-ray crystal structures are reported for the type 2 Cu^(II) C112D/M121E variant of Pseudomonas aeruginosa azurin. The results suggest that Cu^(II) is constrained from interaction with the proximal glutamate; this structural frustration implies a "rack" mechanism for the 290 mV (vs NHE) reduction potential measured at neutral pH. At high pH (~9), hydrogen bonding in the outer coordination sphere is perturbed to allow axial glutamate ligation to Cu^(II), with a decrease in potential to 119 mV. These results highlight the role played by outer-sphere interactions, and the structural constraints they impose, in determining the redox behavior of transition metal protein cofactors.
Additional Information
© 2010 American Chemical Society. Received June 29, 2010. Publication Date (Web): September 29, 2010. Published In Issue October 20, 2010. We thank Prof. Serena DeBeer and Prof. Israel Pecht for insightful discussions. This work was supported by the NIH (DK019038 to H.B.G.). Portions of this research were carried out at the Stanford Synchrotron Radiation Lightsource, a national user facility operated by Stanford University on behalf of the U.S. Department of Energy, Office of Basic Energy Sciences. The SSRL Structural Molecular Biology Program is supported by the Department of Energy, Office of Biological and Environmental Research, and by the National Institutes of Health, National Center for Research Resources, Biomedical Technology Program. The Gordon and Betty Moore Foundation is acknowledged for their support of the Molecular Observatory at Caltech. Supporting Information: Representative redox titration, EPRs across the experimental pH range, and pH 10.0 crystal structure data. This material is available free of charge via the Internet at http://pubs.acs.org.Attached Files
Accepted Version - nihms241422.pdf
Supplemental Material - ja105731x_si_001.pdf
Supplemental Material - ja105731x_si_002.pdb
Supplemental Material - ja105731x_si_003.pdb
Supplemental Material - ja105731x_si_004.pdf
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Additional details
- PMCID
- PMC3375907
- Eprint ID
- 20555
- Resolver ID
- CaltechAUTHORS:20101027-093220417
- NIH
- DK019038
- Gordon and Betty Moore Foundation
- Department of Energy (DOE)
- Created
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2010-11-16Created from EPrint's datestamp field
- Updated
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2021-11-09Created from EPrint's last_modified field