ATP7B

ATP7B encodes a large copper-transporting P-type ATPase expressed most prominently in the liver. The gene lies on chromosome 13q14.3, and its messenger RNA produces a membrane protein of approximately 1,465 amino acids.¹ Like related metal-transporting ATPases, the protein uses energy from ATP hydrolysis to move copper across cellular membranes.

The ATP7B protein contains transmembrane segments, copper-binding regions, and catalytic domains characteristic of P-type ATPases. In hepatocytes, its location changes with cellular copper status: it operates in the trans-Golgi network at ordinary copper levels and relocates toward canalicular membranes when copper is abundant.² This regulated trafficking allows one protein to serve both biosynthetic and detoxifying functions.

ATP7B maintains copper balance by delivering copper for ceruloplasmin production and by enabling excess copper to leave the liver in bile. Copper enters hepatocytes through transport proteins, is distributed among intracellular partners, and is delivered to ATP7B for these two major routes.²

When ATP7B function is substantially reduced, copper cannot be handled normally: incorporation into ceruloplasmin falls while copper accumulates first in the liver and later in organs such as the brain, kidneys, and cornea. The resulting disorder is Wilson disease, an autosomal recessive condition whose manifestations may include hepatitis, cirrhosis, hemolysis, tremor, dystonia, psychiatric changes, and Kayser–Fleischer rings.³ Clinical severity varies widely, even among relatives with the same familial variants.

Pathogenic ATP7B variants include missense, nonsense, splice-altering, and small insertion or deletion changes. More than 500 disease-associated variants have been described, and their frequencies differ among populations; p.His1069Gln is particularly frequent in many European populations, whereas other variants predominate in parts of Asia.¹

Diagnosis does not usually depend on genetic testing alone. Clinicians combine neurological or hepatic findings with serum ceruloplasmin, serum and urinary copper measurements, slit-lamp examination, liver tests, and sometimes hepatic copper quantification; ATP7B sequencing can confirm the molecular cause and support testing of relatives.³ Treatment removes or limits copper with chelating agents such as penicillamine or trientine, or reduces absorption with zinc. Liver transplantation may be required for fulminant or irreversible liver failure.⁴

ATP7B is also relevant before symptoms appear, because biochemical abnormalities can precede overt neurological or liver disease. Predicting an individual course from a single variant remains difficult: modifier genes, environmental factors, residual transporter activity, and the timing of treatment all influence presentation.³

A low ceruloplasmin concentration is supportive but not specific, and some affected people have values within a conventional reference range. Conversely, genetic findings require interpretation because a detected sequence change may be benign, uncertain, or present on only one of the two gene copies. Family screening is therefore valuable when a pathogenic ATP7B variant is established. The protein's copper-responsive movement between intracellular compartments is a notable example of regulated membrane trafficking rather than a permanently fixed transporter location.²

P-type ATPase

A membrane pump that uses ATP-driven phosphorylation to transport ions or other substrates across a membrane.

Ceruloplasmin

The principal copper-carrying protein in blood; ATP7B supplies copper for its maturation in the liver.

Wilson disease

An autosomal recessive disorder caused by impaired copper handling, usually due to pathogenic ATP7B variants.

Kayser–Fleischer ring

A copper-containing ring at the corneal margin that can occur in Wilson disease, especially with neurological involvement.