3D solution structural calculations for yeast silver(I)-substituted metallothionein (MT) and native copper(I) MT were completed using experimentally determined NOE and dihedral angle constraints, in conjunction with experimentally derived metal-to-Cys connectivities for AgMT which were assumed identical for CuMT. For the first 40 residues in both structures, the polypeptide backbone wraps around the metal cluster in two large parallel loops separated by a deep cleft containing the metal cluster. Minor differences between the two structures include differences in hydrogen bonds and the orientation of the N-terminus with the overall protein volume conserved to within 6.5%.
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Acknowledgement: The authors thank Prof. D.R. Winge of the Department of Biochemistry and Medicine, University of Utah Medical Center, Salt Lake City, Utah, for providing the protein for the NMR studies which made the present structure calculations possible. They also thank Prof. Axel Briinger for helpful discussions on the use of X-PLOR and Kevin Gardner for sharing software that facilitated structure analysis. Very thoughtful criticisms and comments from Yuxin Hua in this laboratory are also gratefully acknowledged. This work was supported in part by National Institutes of Health grant DK18778. NMR instrumentation and computational facilities were provided from NIH (RR03475), NSF (DMB8610557) and ACS (RD259).
- Nuclear magnetic resonance
- Protein structure
- Yeast metallothionein