Volume 58, Issue 7 pp. 1099-1103

Generating isomorphous heavy-atom derivatives by a quick-soak method. Part II: phasing of new structures

Peter D. Sun

Peter D. Sun

Structural Immunology Section, Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 12441 Parklawn Drive, Rockville, MD 20852, USA

Search for more papers by this author
Sergei Radaev

Sergei Radaev

Structural Immunology Section, Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 12441 Parklawn Drive, Rockville, MD 20852, USA

Search for more papers by this author
First published: 15 June 2004
Citations: 2
Peter D. Sun, e-mail: [email protected]

Abstract

A quick-soak method has been applied to generate de novo heavy-atom phasing to solve two new protein structures, a type II transforming growth factor β receptor (TBRII) and a natural killer cell receptor–ligand complex, NKG2D–ULBP3. In the case of TBRII, a crystal derivatized for only 10 min in saturated HgCl2 provided adequate phasing for structure determination. Comparison between HgCl2 derivatives generated by 10 min soaking and by 12 h soaking revealed similar phasing statistics. The shorter soak, however, resulted in a derivative more isomorphous to the native than the longer soak as judged by changes in the unit-cell parameter a upon derivatization as well as by the quality of a combined SIRAS electron-density map. In the case of the NKG2D–ULBP3 structure, all overnight soaks in heavy-atom solutions resulted in crystal lattice disorder and only the quick soaks preserved diffraction. Despite fragile lattice packing, the quick-soaked K2PtCl4 derivative was isomorphous with the native crystal and the electron-density map calculated from combined SIR and MAD phases is better than that calculated from MAD phases alone. Combined with mass-spectrometry-assisted solution heavy-atom derivative screening and the use of synchrotron radiation, the quick-soak derivatization has the potential to transform the time-consuming conventional heavy-atom search into a real-time `on-the-fly' derivatization process that will benefit high-throughput structural genomics.

The full text of this article hosted at iucr.org is unavailable due to technical difficulties.