Ta6Br14 is a useful cluster compound for isomorphous replacement in protein crystallography
- 1 March 1994
- journal article
- Published by International Union of Crystallography (IUCr) in Acta Crystallographica Section D-Biological Crystallography
- Vol. 50 (2) , 186-191
- https://doi.org/10.1107/s0907444993009679
Abstract
The metal cluster Ta(6)Br(14) has been used to prepare heavy-metal derivatives of two large proteins, ribulose-1,5-bisphosphate carboxylase/oxygenase and transketolase. In both cases, this cluster compound produced a single-site derivative for which a difference Patterson map, calculated to 5.5 A resolution, could be solved straightforwardly. Ta(6)Br(14) provided enough phase information to unambiguously locate the heavy-atom positions in other multiple-site derivatives. In transketolase, the heavy-metal complex binds at the surface of the protein in a dominantly hydrophobic pocket. In ribulose bisphosphate carboxylase/oxygenase, it binds between two molecules in the crystal lattice. There are negatively charged glutamic and/or aspartic acid residues in the vicinity of the bound clusters. Ta(6)Br(14) is useful over a wide range of pH. For large proteins and/or large unit cells, this compound should be included in the initial screening for heavy-metal derivatives.Keywords
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