Thyroxine-binding globulin

SERPINA7
Available structures
PDB	Ortholog search: PDBe RCSB
List of PDB id codes
	2CEO, 2RIV, 2RIW, 2XN3, 2XN5, 2XN6, 2XN7, 4X30, 4YIA
Identifiers
Aliases	SERPINA7, TBG, serpin family A member 7, Thyroxine-binding globulin，TBG, TBGQTL
External IDs	OMIM: 314200; MGI: 3041197; HomoloGene: 20113; GeneCards: SERPINA7; OMA:SERPINA7 - orthologs
Gene location (Human)
Chr.	X chromosome (human)
End	106,038,727 bp
Gene location (Mouse)
Chr.	X chromosome (mouse)
End	137,985,985 bp
RNA expression pattern
	Top expressed in
	liver; ; right lobe of liver; ; skin of thigh; ; renal cortex; ; body of pancreas; ; small intestine; ; human kidney; ; fallopian tube; ; rectum; ; lower lobe of lung;
	Top expressed in
	liver; ; left lobe of liver; ; embryo; ; islet of Langerhans; ; sexually immature organism; ; epithelium of stomach; ; spermatid; ; lumbar subsegment of spinal cord; ; thymus; ; ureter;
	More reference expression data
	n/a
Gene ontology
Molecular function	serine-type endopeptidase inhibitor activity;
Cellular component	extracellular exosome; extracellular region; extracellular space;
Biological process	thyroid hormone transport; negative regulation of endopeptidase activity;
	Sources:Amigo / QuickGO
Orthologs
	6906
	331535
	ENSG00000123561
	ENSMUSG00000031271
	P05543
	P61939
	NM_000354
	NM_177920; NM_001382371; NM_001382372
	NP_000345
	NP_808588; NP_001369300; NP_001369301
	Wikidata
View/Edit Human	View/Edit Mouse

Thyroxine-binding globulin (TBG) is a globulin protein encoded by the SERPINA7 gene in humans. TBG binds thyroid hormones in circulation. It is one of three transport proteins (along with transthyretin and serum albumin) responsible for carrying the thyroid hormones thyroxine (T₄) and triiodothyronine (T₃) in the bloodstream. Of these three proteins, TBG has the highest affinity for T₄ and T₃ but is present in the lowest concentration relative to transthyretin and albumin, which also bind T3 and T4 in circulation. Despite its low concentration, TBG carries the majority of T₄ in the blood plasma. Due to the very low concentration of T₄ and T₃ in the blood, TBG is rarely more than 25% saturated with its ligand. Unlike transthyretin and albumin, TBG has a single binding site for T₄/T₃. TBG is synthesized primarily in the liver as a 54-kDa protein. In terms of genomics, TBG is a serpin; however, it has no inhibitory function like many other members of this class of proteins.