Abstract
Metal ions play essential roles in many aspects of biological chemistry. Detecting their presence and location in proteins and cells is important for understanding biological function. Conventional structural methods such as X-ray crystallography and cryo-transmission electron microscopy can identify metal atoms on protein only if the protein structure is solved to atomic resolution. We demonstrate here the detection of isolated atoms of Zn and Fe on ferritin, using cryogenic annular dark-field scanning transmission electron microscopy (cryo-STEM) coupled with single-particle 3D reconstructions. Zn atoms are found in a pattern that matches precisely their location at the ferroxidase sites determined earlier by X-ray crystallography. By contrast, the Fe distribution is smeared along an arc corresponding to the proposed path from the ferroxidase sites to the mineral nucleation sites along the twofold axes. In this case the single-particle reconstruction is interpreted as a probability distribution function based on the average of individual locations. These results establish conditions for detection of isolated metal atoms in the broader context of electron cryo-microscopy and tomography.
| Original language | English |
|---|---|
| Pages (from-to) | 11139-11144 |
| Number of pages | 6 |
| Journal | Proceedings Of The National Academy Of Sciences Of The United States Of America-Physical Sciences |
| Volume | 114 |
| Issue number | 42 |
| DOIs | |
| Publication status | Published - 17 Oct 2017 |
Funding
We are grateful to Bart De Strooper for support during the project, to Jose Maria Carazo and Carlos Oscar Sanchez for discussions on data verification, and to Akif Tezcan for discussion on ferritin structures. This work was funded in part by a grant from the Israel Science Foundation (Grant 1285/14). Support from the Henry Chanoch Krenter Institute for Biomedical Imaging and Genomics, the Gerhardt M. J. Schmidt Minerva Center for Supramolecular Architecture, and the Irving and Cherna Moskowitz Center for Nano and Bionano Imaging is also gratefully acknowledged. The laboratory of M.E. has benefited from the historical generosity of the Harold Perlman family. Author contributions: N.E., G.B., I.S., and M.E. designed research; N.E. and L.H. performed research; G.B. and L.H. contributed new reagents/analytic tools; N.E., L.H., and M.E. analyzed data; and N.E., G.B., L.H., I.S., and M.E. wrote the paper.
All Science Journal Classification (ASJC) codes
- General