Diverse roles of the metal binding domains and transport mechanism of copper transporting P-type ATPases

Abstract

Copper transporting P-type (P_1B-1-) ATPases are essential for cellular homeostasis. Nonetheless, the E1-E1P-E2P-E2 states mechanism of P_1B-1-ATPases remains poorly understood. In particular, the role of the intrinsic metal binding domains (MBDs) is enigmatic. Here, four cryo-EM structures and molecular dynamics simulations of a P_1B-1-ATPase are combined to reveal that in many eukaryotes the MBD immediately prior to the ATPase core, MBD^-1, serves a structural role, remodeling the ion-uptake region. In contrast, the MBD prior to MBD^-1, MBD^-2, likely assists in copper delivery to the ATPase core. Invariant Tyr, Asn and Ser residues in the transmembrane domain assist in positioning sulfur-providing copper-binding amino acids, allowing for copper uptake, binding and release. As such, our findings unify previously conflicting data on the transport and regulation of P_1B-1-ATPases. The results are critical for a fundamental understanding of cellular copper homeostasis and for comprehension of the molecular bases of P_1B-1-disorders and ongoing clinical trials.