Visualising shared-ligand intermediates of metal exchange

Visualized by Rapid Freeze Quench and Selenium EXAFS of Se-Labeled Metallochaperones. A Paradigm for Studying Copper-Mediated Host-Pathogen Interactions.

Mammalian hosts defend against invading pathogens via the import of toxic concentrations of copper into the phagolysosome. To combat this host-defense strategy, gram negative pathogens respond via sophisticated copper export systems which are able to neutralize the copper onslaught2. Chemical mechanisms of metal exchange between protein components of metal exporters are thus important factors in understanding pathogenic virulence and are believed to occur via formation of intermediates in which the metal is coordinated by ligands derived from each partner.  However, since these ligand sets are often similar (or even identical), following the kinetics of transfer has been challenging, and has required the development of sophisticated spectroscopic approaches.

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Image: Middle: Se EXAFS Fourier transforms at increasing time points for the reaction of SeM-labeled apo-CusF with unlabeled Cu(I)-loaded CusB.  Left and right: in silico models of the proposed protein-protein interface and shared-ligand intermediate.