Exploring the interaction between the human copper transporter, CTR1, c-terminal domain and a methionine motif in the presence of Cu(I) and Ag(I) ions, using EPR spectroscopy

Abstract

The essentiality and toxicity of copper in human, yeast, and bacteria cells requires precise mechanisms for acquisition, intimately linked to controlled distribution, which have yet to be fully understood. Herein, we utilise continuous wave and pulsed electron paramagnetic resonance (EPR) spectroscopy to explore one aspect in the controlled copper transportation mechanism. This was achieved by probing structural changes that occur in the c-terminal domain of the human copper transporter, CTR1, upon interacting with a methionine segment. The copper transporter CTR1 transports Cu(I) and Ag(I) ions to various intracellular pathways. Methionine motifs are methionine-rich metal binding segments found in many proteins involved in the transportation of copper ions to other cellular pathways. They are also found to bind Ag(I) with an affinity comparable to Cu(I). This study indicates that the methionine motif experiences conformational changes in the presence of the CTR1 c-terminal domain. These structural changes are dependent on the nature of the metal ion, Cu(I) vs. Ag(I). In addition, the data collected in this study emphasise how important the cysteine residue of the CTR1 c-terminal domain is to a correct conformational state of the target metal binding site.

Keywords:

• electron paramagnetic resonance
• copper transport
• site-directed spin labelling
• methionine segments

Acknowledgement

The authors thank Prof. Byk and Dr. Rahimipour (the Chemistry Department at Bar-Ilan University) for many helpful discussions. This study was supported by the Israel Science Foundation, grant no. 280/12.