Cysteine contributions to metal binding preference for Zn/Cd in the beta-domain of metallothionein.
Previous studies showed that metals in the beta-domain of metallothionein (MT) are more readily exchangeable and the level of avidity is site specific. This is reflected by energy differences computed with a series of simulated structures derived from X-ray crystallography. In this study, we examined further the contribution of each of the nine cysteines in the beta-domain. By semi-empirical MNDO calculations, we observed that the relative average binding strength is the strongest for Cys21 to Cd[M4] and for Cys26 to Zn[M3], except for the bridging cysteines. These results suggest that binding site preference for Zn/Cd is determined by binding strength between specific cysteines and metal ion species.
Chang
C C
CC
Department of Life Sciences, National Tsing Hua University, Taiwan, Republic of China.
Liao
W F
WF
Huang
P C
PC
D002104:Cadmium / Q000378:metabolism*; D003545:Cysteine / Q000737:chemistry*; D008668:Metallothionein / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D013816:Thermodynamics; D015032:Zinc / Q000378:metabolism*
D002104:Cadmium; D008668:Metallothionein; D015032:Zinc; D003545:Cysteine