Probing the structural flexibility of the human copper metallochaperone Atox1 dimer and its interaction with the CTR1 c-terminal domain.

Both the essentiality and the toxicity of copper in human, yeast, and bacteria cells require precise mechanisms for acquisition, intimately linked to controlled distribution, which have yet to be fully understood. This work explores one aspect in the copper cycle, by probing the interaction between the human copper chaperone Atox1 and the c-terminal domain of the copper transporter, CTR1, using electron paramagnetic resonance (EPR) spectroscopy and circular dichroism (CD). The data collected here shows that the Atox1 keeps its dimer nature also in the presence of the CTR1 c-terminal domain; however, two geometrical states are assumed by the Atox1. One is similar to the geometrical state reported by the crystal structure, while the latter has not yet been constructed. In the presence of the CTR1 c-terminal domain, both states are assumed; however, the structure of Atox1 is more restricted in the presence of the CTR1 c-terminal domain. This study also shows that the last three amino acids of the CTR1 c-terminal domain, HCH, are important for maintaining the crystal structure of the Atox1, allowing less structural flexibility and improved thermal stability of Atox1.