Globuline liant la thyroxine

Structure de la TBG montrant lathyroxineliée (PDB2CEO).

Laglobuline liant la thyroxine(TBG,de l'anglais:thyroxine-binding globulin) est l'une des trois classes deprotéinestransporteuses deshormones thyroïdiennesdans lesang,les deux autres étant latransthyrétine(TTR) et lesalbuminessériques.La TGB est celle des trois qui possède l'affinité la plus élevée pour lathyroxine(T₄) et latriiodothyronine(T₃), mais, contrairement à ces deux autres classes de protéines, elle ne possède qu'un seul site liant la T₄ou la T₃par molécule. C'est également celle dont la concentration dans le sang est la plus faible. Malgré cela, la TBG transporte l'essentiel de la T₄dans le sang. Le taux sanguin de T₄et de T₃est si faible que la TBG est rarement occupée à plus de 25 % par une molécule d'hormone thyroïdienne.

La TBG est produite essentiellement dans lefoiecomme une protéine de 54kDa.D'un point de vuegénomique,la TBG est uneserpine,mais elle ne possède pas de fonction inhibitrice comme de nombreuses autres protéines de ce type.

Notes et références

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