thyroxine-binding globulin; Serpin A7; T4-binding globulin (SERPINA7, TBG)

Function: - TBG is one of the 3 major plasma thyroid hormone-binding proteins (prealbumin & albumin are the other 2 - the majority of thyroid hormone is bound by TBG (70% of T4 & 75-80% of T3) - each TBG molecule binds one molecule of T3 or T4 - prealbumin binds 10% of T4 & 10% of T3 Structure: belongs to the serpin family Compartment: secreted Expression: - expressed by the liver (hepatocytes) & secreted into plasma Polymorphism: - two qualitative TBG variants occur in particular populations - TBG-A is found in 40% of Australian aborigines - it has reduced affinity for thyroxine & triiodothyroxine & increased susceptibility to inactivation by heat or acid - TBG-S ('s' for slow shift on isoelectic focusing) is found in blacks, Eskimos, Melanesians, Polynesians & Indonesians - not found in Caucasians - TBG-S is slightly more thermolabile Pathology: - defects in SERPINA7 are a cause of thyroxine-binding globulin deficiency

Related

protein disulfide isomerase (cellular thyroid hormone binding protein, prolyl 4-hydroxylase subunit beta, P4HB, ERBA2L, PDI, PDIA1, PO4DB) thyroxine-binding globulin in serum/plasma

General

alpha 1 globulin glycoprotein

Properties

SIZE: entity length = 415 aa MW = 46 kD COMPARTMENT: plasma MOTIF: signal sequence {1-20} N-glycosylation site {N36} N-glycosylation site {N99} N-glycosylation site {N165} N-glycosylation site {N253} binding site SITE: 293-293 FOR-BINDING-OF: thyroxine binding site SITE: 398-398 FOR-BINDING-OF: thyroxine

Database Correlations

OMIM 314200 MORBIDMAP 314200 UniProt P05543 Pfam PF00079 Entrez Gene 6906 Kegg hsa:6906

References

UniProt :accession P05543