Krill Prize Laureate 2015
Exploring the human copper transfer mechanism by electron paramagnetic resonance spectroscopy
Sharon Ruthstein’s research aims to shed light on biological pathways that involve metal ions by using Electron Paramagnetic Resonance Spectroscopy (EPR). More than 30% of all proteins in the cell exploit one or more metals to perform their specific functions, and over 40% of all enzymes contain metals. Metals are commonly found as natural constituents of proteins; however, many metal ions can be toxic when free in biological fluids. Hence, humans and microorganisms have evolved a regulatory machinery to acquire, utilize traffic, detoxify, and otherwise manage the intracellular and extracellular concentrations and types of metal ions. Despite the high regulation of metal ions in the human body, diseases such as Menkes, Wilson, Alzheimer’s, Parkinson’s and Prion’s have been linked with metal binding to proteins. It is therefore vitally important to understand each step of the copper cycle, in order to build a fundamental understanding of sources of the disruption of copper homeostasis that can lead eventually to neurological diseases and disorders. Dr. Ruthstein’s lab is looking into some of the least understood biological processes that are related to metal ion transport and intracellular distribution.
Some of the ongoing projects in her lab are:
(i) Explore metal ion import and export mechanism of the human copper transporter CTR1, from the blood carrier copper protein, albumin, through the CTR1, and to the metallochaperone Atox1.
(ii) Help understand metal binding mechanism of various metal sensors in bacterial cells (CueR and CsoR systems), in order to shed light on the metal regulatory machinery of the bacteria.
(iii) Explore the role of the copper efflux system in E.coli, in particular the Cus system.
(iv) Characterize the role of copper and mutations on the aggregation and folding of proteins, in order to illuminate the microscopic origins of neurological diseases.
To comprehend such processes it is necessary to be sensitive to the structural changes that occur in the protein upon metal binding. The main biophysical tool that is used in the lab of Dr. Ruthstein’s lab is pulsed electron Paramagnetic Resonance (EPR) spectroscopy. The power of EPR lies in the sensitivity to both atomic level changes and nanoscale fluctuations. EPR can characterize properties such as redox state and ligand geometry for different functional states of the protein. The data collected by the EPR experiments is complement by various other biophysical and biochemical approaches, as well as computational methods, such as: CD, NMR, run-off transcription assays, ultra-centrifuge experiments, ITC, and MD simulations, to provide a complete picture on the cellular copper cycle. Dr. Ruthstein’s lab also has several fruitful collaborations in Israel and abroad. One collaboration is with Prof. Hamza (University of Maryland) where the heme’s transfer mechanism by the metallochaperone, HRG-3, in c.elegans is being explored. Additional collaboration is with the lab of Prof. Haim Cohen, Ariel University/BGU. In this collaboration, EPR spectroscopy is used together with other physical methods to characterize the surface radical’s nature in coals. It was revealed that several radical species are observed, and their nature is dependent on the coal rank, and micropores surface area. This work was summarized in three PCCP papers, and the experimental work was published in JoVE. Other collaborations are together with Prof. Lellouche and Dr. Goobes on characterizing the oxidation process of graphene’s surfaces. Additional collaboration is together with Dr. Lior Elbaz (BIU). In this study, Dr. Ruthstein is studying at the molecular level the coordination of heme molecules on graphene surfaces, as well as the interaction of the studied graphene surfaces with oxygen molecules.