ABCD4

ABCD4 is a gene that in humans encodes a protein which is involved in the import of vitamin B12 into the mitochondria. The protein is a member of the superfamily of ATP-binding cassette (ABC) transporters. ABC proteins transport various molecules across extra- and intra-cellular membranes.

Function

The ABCD4 protein is a member of the peroxisomal ABC transporter subfamily, which includes ABCD1, ABCD2, and ABCD3. The ABCD4 protein is involved in the transport of cobalamin, also known as vitamin B12, into the mitochondria. Cobalamin is a water-soluble vitamin with a key role in the normal functioning of the brain and nervous system, and for the formation of blood.

Clinical significance

Mutations in the ABCD4 gene are associated with the rare genetic disorder methylmalonic aciduria and homocystinuria, cblJ type. This disorder is characterized by decreased levels of the coenzyme adenosylcobalamin, which leads to an accumulation of methylmalonic acid and homocysteine in the blood and urine. Symptoms of this disorder include developmental delay, failure to thrive, hypotonia, and seizures.

See also

• ATP-binding cassette transporter
• Vitamin B12
• Methylmalonic aciduria and homocystinuria, cblJ type