title: Evolution of thyroid hormone distributor proteins.
abstract: Thyroid hormones (THs) are evolutionarily old hormones, having effects on metabolism in bacteria, invertebrates and vertebrates. THs bind specific distributor proteins (THDPs) to ensure their efficient distribution through the blood and cerebrospinal fluid in vertebrates. Albumin is a THDP in the blood of all studied species of vertebrates, so may be the original vertebrate THDP. However, albumin has weak affinity for THs. Transthyretin (TTR) has been identified in the blood across different lineages in adults vs juveniles. TTR has intermediate affinity for THs. Thyroxine-binding globulin has only been identified in mammals and has high affinity for THs. Of these THDPs, TTR is the only one known to be synthesised in the brain and is involved in moving THs from the blood into the cerebrospinal fluid. We analysed the rates of evolution of these three THDPs: TTR has been most highly conserved and albumin has had the highest rate of divergence.
authors.affiliation: School of Science, RMIT University, Bundoora, 3083 Victoria, Australia. Electronic address: s3163725@student.rmit.edu.au.
authors.forename: Thomas R
authors.initials: TR
authors.lastname: McLean
authors.affiliation: School of Health and Biomedical Sciences, RMIT University, Bundoora, 3083 Victoria, Australia. Electronic address: michelle.rank@rmit.edu.au.
authors.forename: Michelle M
authors.initials: MM
authors.lastname: Rank
authors.affiliation: School of Science, RMIT University, Bundoora, 3083 Victoria, Australia. Electronic address: peter.smooker@rmit.edu.au.
authors.forename: Peter M
authors.initials: PM
authors.lastname: Smooker
authors.affiliation: School of Health and Biomedical Sciences, RMIT University, Bundoora, 3083 Victoria, Australia. Electronic address: samantha.richardson@rmit.edu.au.
authors.forename: Samantha J
authors.initials: SJ
authors.lastname: Richardson
mesh_terms: D000418:Albumins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D000818:Animals; D017124:Conserved Sequence; D019143:Evolution, Molecular; D015870:Gene Expression; D006801:Humans; D008958:Models, Molecular; D010802:Phylogeny; D011228:Prealbumin / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D017433:Protein Structure, Secondary; D021381:Protein Transport; D012641:Selection, Genetic; D013963:Thyroid Hormones / Q000235:genetics / Q000378:metabolism*; D056825:Thyroxine-Binding Globulin / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D000418:Albumins; D011228:Prealbumin; D013963:Thyroid Hormones; D056825:Thyroxine-Binding Globulin
keywords: Albumin; Positive selection; Protein evolution; Thyroid hormone; Thyroxine-binding globulin; Transthyretin