X-ray absorption spectra of the oxidized and reduced forms of C112D azurin from Pseudomonas aeruginosa
- Stanford Univ., CA (United States). Dept. of Chemistry
- California Inst. of Tech., Pasadena, CA (United States). Beckman Inst.
- Stanford Synchrotron Radiation Lab., CA (United States)
The oxidized and reduced forms of a mutant of Pseudomonas aeruginosa azurin, in which the Cys112 has been replaced by an aspartate, have been studied by X-ray absorption spectroscopy. It is well established that the characteristic {approximately}600 nm absorption feature of blue copper proteins is due to the S(Cys112) 3p{pi} {r_arrow} Cu 3d{sub x{sup 2}{minus}y{sup 2}} charge-transfer transition. While other mutagenesis studies have involved the creation of an artificial blue copper site, the present work involves a mutant in which the native blue copper site has been destroyed, thus serving as a direct probe of the importance of the copper-thiolate bond to the spectroscopy, active site structure, and electron-transfer function of azurin. Of particular interest is the dramatic decrease in electron-transfer rates, both electron self-exchange and intramolecular electron transfer to ruthenium-labeled sites, which is observed in the mutant. These changes may be a reflection of significant differences in electronic coupling into the protein matrix and/or in the reorganization energy. These effects can be probed by the use of Cu K-edge X-ray absorption spectroscopy, the results of which indicate both a decrease in the covalency of the active site and an expansion of {approximately}0.2 {angstrom} in the Cu coordination sphere trigonal plane upon reduction of the C112D mutant.
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- OSTI ID:
- 329265
- Journal Information:
- Inorganic Chemistry, Journal Name: Inorganic Chemistry Journal Issue: 3 Vol. 38; ISSN 0020-1669; ISSN INOCAJ
- Country of Publication:
- United States
- Language:
- English
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