Resonant X-Ray Scattering and Absorption for the Global and Local Structures of Cu-modified Metallothioneins in Solution
Resource
Biophysical Journal 97 (2): 609-617
Journal
Biophysical Journal
Pages
609-617
Date Issued
2009
Date
2009
Author(s)
Li, Meiyi
Huang, Yu-Shan
Jeng, U-Ser
Hsu, I-Jui
Wu, Yew Chung Sermon
Lai, Ying-Huang
Su, Chiu-Hun
Lee, Jyh-Fu
Wang, Yu
Chang, Chia-Ching
Abstract
With Cd and Zn metal ions removed from the native rabbit-liver metallothionein upon unfolding, Cu-modified metallothioneins (Cu-MTs) were obtained during refolding in solutions containing Cu(I) or Cu(II) ions. X-ray absorption near-edge spectroscopic results confirm the respectively assigned oxidation states of the copper ions in Cu(I)-MT and Cu(II)-MT. Global and local structures of the Cu-MTs were subsequently characterized by anomalous small-angle x-ray scattering (ASAXS) and extended x-ray absorption fine structure. Energy-dependent ASAXS results indicate that the morphology of Cu(II)-MT resembles that of the native MT, whereas Cu(I)-MT forms oligomers with a higher copper content. Both dummy-residue simulation and model-shape fitting of the ASAXS data reveal consistently rodlike morphology for Cu(II)-MT. Clearly identified Cu-S, Cu-O, and Cu-Cu contributions in the extended x-ray absorption fine structure analysis indicate that both Cu(I) and Cu(II) ions are bonded with O and S atoms of nearby amino acids in a four-coordination environment, forming metal clusters smaller than metal thiolate clusters in the native MT. It is demonstrated that a combination of resonant x-ray scattering and x-ray absorption can be particularly useful in revealing complementary global and local structures of metalloproteins due to the atom specific characteristics of the two techniques.
Type
journal article
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