Resonant x-ray scattering and absorption for the global and local structures of Cu-modified metallothioneins in solution.
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.
Li
Meiyi
M
Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu, Taiwan.
Huang
Yu-Shan
YS
Jeng
U-Ser
US
Hsu
I-Jui
IJ
Sermon Wu
Yewchung
Y
Lai
Ying-Huang
YH
Su
Chiu-Hun
CH
Lee
Jyh-Fu
JF
Wang
Yu
Y
Chang
Chia-Ching
CC
D000042:Absorption; D000818:Animals; D001059:Apoproteins / Q000737:chemistry / Q000378:metabolism; D003300:Copper / Q000737:chemistry* / Q000378:metabolism*; D008668:Metallothionein / Q000737:chemistry* / Q000378:metabolism*; D008958:Models, Molecular; D010084:Oxidation-Reduction; D011487:Protein Conformation; D011489:Protein Denaturation; D020673:Protein Renaturation; D011817:Rabbits; D053838:Scattering, Small Angle; D012996:Solutions; D014961:X-Ray Diffraction
D001059:Apoproteins; D012996:Solutions; D003300:Copper; D008668:Metallothionein