Transthyretin_like. This domain is present in the transthyretin-like protein (TLP) family which includes transthyretin (TTR) and a transthyretin-related protein called 5-hydroxyisourate hydrolase (HIUase). TTR and HIUase are homotetrameric proteins with each subunit consisting of eight beta-strands arranged in two sheets and a short alpha-helix. The central channel of the tetramer contains two independent binding sites, each located between a pair of subunits. TTR transports thyroid hormones and retinol in the blood serum of vertebrates while HIUase catalyzes the second step in a three-step ureide pathway. TTRs are highly conserved and found only in vertebrates while the HIUases are found in a wide range of bacterial, plant, fungal, slime mold and vertebrate organisms.
Structure:1IE4_A; Rattus norvegicus transthyretin binds two molecules of thyroxine; this homotetrameric thyretin structure contains two independent binding sites within the central core of the tetramer, each formed by a pair of monomers. Contacts determined at 3.5 Angstroms. - View structure with Cn3D