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Location‐specific quantification of protein‐bound metal ions by X‐ray anomalous dispersion: Q‐XAD
Author(s) -
Griese Julia J.,
Högbom Martin
Publication year - 2019
Publication title -
acta crystallographica section d
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.374
H-Index - 138
ISSN - 2059-7983
DOI - 10.1107/s2059798319009926
Subject(s) - metalloprotein , metal , chemistry , transition metal , metal ions in aqueous solution , dispersion (optics) , crystallography , ion , binding site , materials science , analytical chemistry (journal) , chromatography , physics , biochemistry , organic chemistry , optics , catalysis
Here, a method is described which exploits X‐ray anomalous dispersion (XAD) to quantify mixtures of metal ions in the binding sites of proteins and can be applied to metalloprotein crystals of average quality. This method has successfully been used to study site‐specific metal binding in a protein from the R2‐like ligand‐binding oxidase family which assembles a heterodinuclear Mn/Fe cofactor. While previously only the relative contents of Fe and Mn in each metal‐binding site have been assessed, here it is shown that the method can be extended to quantify the relative occupancies of at least three different transition metals, enabling complex competition experiments. The number of different metal ions that can be quantified is only limited by the number of high‐quality anomalous data sets that can be obtained from one crystal, as one data set has to be collected for each transition‐metal ion that is present (or is suspected to be present) in the protein, ideally at the absorption edge of each metal. A detailed description of the method, Q‐XAD, is provided.