Coordination of Bi3+ to metal-free metallothionein: spectroscopy and density functional calculation of structure, coordination, and electronic excitations.
Understanding the structure of mammal Bi-containing metallothionein-2 (Bi-MT2) is of great physiological significance due to the importance of Bi-MT2 in alleviating adverse effect of anti-cancer drugs. A unique feature of rabbit liver Bi-MT2 is the metal-oxygen bond (BiO), which is absent in well-characterized Zn-MT2 and Cd-MT2. However, the ligand contributing to the BiO bonding in Bi-MT2 remains unidentified. In this study, the coordination of Bi(3+) to rabbit liver metal-free metallothionein was investigated using both experimental and theoretical methods. UV-visible and circular dichroism spectra indicate that Bi-MT2 has a different secondary structure from those of Zn-MT2 and Cd-MT2. Three possible Bi(3+) coordination structures in Bi(7)-MT2 and relative binding free energies were calculated using the density functional theory. Absorption spectra corresponding to these coordination structures were evaluated by time-dependent density functional theory. Our computation results are consistent with the UV-vis spectroscopic data and strongly suggest that the carboxyl group in the aspartic acid residues contributes to the BiO bond formation.
College of Chemistry and Chemical Engineering, Central South University, Changsha 410083, PR China.
Yonghui
Y
He
Shu
S
Chen
Younian
Y
Liu
Yizeng
Y
Liang
Juan
J
Xiang
Deyin
D
Wu
Feimeng
F
Zhou
D000818:Animals; D001224:Aspartic Acid / Q000737:chemistry*; D001665:Binding Sites; D001729:Bismuth / Q000737:chemistry*; D002104:Cadmium / Q000737:chemistry; D002942:Circular Dichroism; D056831:Coordination Complexes / Q000737:chemistry*; D004583:Electrons; D007700:Kinetics; D008099:Liver / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008668:Metallothionein / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry*; D017433:Protein Structure, Secondary; D011789:Quantum Theory; D011817:Rabbits; D013056:Spectrophotometry, Ultraviolet; D013816:Thermodynamics; D015032:Zinc / Q000737:chemistry
D056831:Coordination Complexes; D002104:Cadmium; D001224:Aspartic Acid; D008668:Metallothionein; D015032:Zinc; D010100:Oxygen; D001729:Bismuth