Transthyretin

Transthyretin (TTR) is a protein that in humans is encoded by the TTR gene. It is a transport protein in the serum and cerebrospinal fluid that carries the thyroid hormone thyroxine (T4) and retinol-binding protein bound to retinol.

Structure

Transthyretin is a tetramer of four identical subunits. Each subunit is a polypeptide chain made up of 127 amino acid residues. The four subunits form a central channel that can bind up to two molecules of thyroxine.

Function

The primary role of transthyretin is to transport thyroxine and retinol throughout the body. It binds to thyroxine in a 1:1 ratio and to retinol-binding protein in a 2:1 ratio. Transthyretin is synthesized primarily in the liver, but also in the choroid plexus of the brain and the retina.

Clinical significance

Mutations in the TTR gene can lead to various forms of transthyretin-related hereditary amyloidosis, a group of diseases characterized by the abnormal deposition of transthyretin amyloid fibrils in various tissues and organs. The most common form is familial amyloid polyneuropathy (FAP), which primarily affects the peripheral nervous system.

See also

• Amyloidosis
• Familial amyloid polyneuropathy
• Thyroxine-binding globulin
• Retinol-binding protein