Human Transthyretin/TTR, Tag Free Protein (HA211085)

Thyroid hormone-binding protein. Probably transports thyroxine from the bloodstream to the brain. Tetramer dissociation and partial unfolding leads to the formation of aggregates and amyloid fibrils. Small molecules that occupy at least one of the thyroid hormone binding sites stabilize the tetramer, and thereby stabilize the native state and protect against misfolding and the formation of amyloid fibrils. Two binding sites for thyroxine are located in the channel. Less than 1% of plasma prealbumin molecules are normally involved in thyroxine transport. L-thyroxine binds to the transthyretin by an order of magnitude stronger than does the triiodo-L-thyronine. Thyroxine-binding globulin is the major carrier protein for thyroid hormones in man. About 40% of plasma transthyretin circulates in a tight protein-protein complex with the plasma retinol-binding protein (RBP). The formation of the complex with RBP stabilizes the binding of retinol to RBP and decreases the glomerular filtration and renal catabolism of the relatively small RBP molecule. There is evidence for 2 binding sites for RBP, one possibly being a region that includes Ile-104, located on the outer surface of the transthyretin molecule.