ジャーナル: Proc Natl Acad Sci U S A / 年: 2017 タイトル: Detection of isolated protein-bound metal ions by single-particle cryo-STEM. 著者: Nadav Elad / Giuliano Bellapadrona / Lothar Houben / Irit Sagi / Michael Elbaum / 要旨: 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 ...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.
名称: Human heavy chain ferritin with Zn / タイプ: complex / ID: 1 / 親要素: 0 / 含まれる分子: #1 詳細: Bacterially expressed and purified human heavy chain ferritin mixed with a 48 fold molar excess of Zn(II)SO4
詳細: The initial model was prepared from the human ferritin heavy chain crystal structure from which all heavy atoms were removed. The protein PDB coordinates were converted to structure factors ...詳細: The initial model was prepared from the human ferritin heavy chain crystal structure from which all heavy atoms were removed. The protein PDB coordinates were converted to structure factors and low pass filtered to 4 nm.