Mechanistic Insights into the Wilson Disease Protein MBD6 and Its Interaction with the Chaperone Atox1 underlying the G626A Mutation

The human transporter ATP7B plays a critical role in maintaining hepatic copper homeostasis, a process mediated by the specific interaction between its metal binding domain (MBD) and copper chaperone Atox1. The G626A mutation in MBD are known to cause the fatal hepatoneurological disorder Wilson disease (WD). However, the interaction mode between MBD and Atox1, as well as the molecular mechanism underlying WD-associated mutations impair copper transport, remains poorly understood. To bridge this gap, we conducted molecular dynamics simulations and free energy calculations to explore the dynamic properties of Atox1-MBD complex. Our results indicate that Atox1-Cu(I) binding to MBD triggers spontaneous protonation of C575 and C578, markedly enhancing the dynamic stability of Atox1–MBD complex. Furthermore, we have identified a critical interacting network mediated by hydrogen bonds and electrostatic interactions, and delineate how G626A mutation disrupts the key hydrogen bond between G626 and R21. Our study provides mechanistic insights into the dynamics of Atox1-MBD complex during Cu(I) transfer, establishing a link between WD-associated mutation and the functional deficit.