ATP7B is a gene that provides instructions for making a protein involved in copper transport within the body. This protein helps regulate copper levels by facilitating its movement into and out of cells, ensuring that the body maintains a proper balance of this essential mineral. Mutations in the ATP7B gene can lead to a condition known as Wilson's disease, which causes excessive copper accumulation in the liver, brain, and other tissues. This buildup can result in serious health issues, including liver damage and neurological problems, highlighting the importance of the ATP7B protein in maintaining copper homeostasis.