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sex hormone-binding globulin; SHBG; Sex steroid-binding protein; SBP; testis-specific androgen-binding protein; ABP; testosterone-estrogen-binding globulin; testosterone-estradiol-binding globulin; TeBG (SHBG)
Function:
- androgen transport protein, but may also be involved in receptor mediated processes
- functions as a homodimer
- each dimer binds one molecule of steroid
- specific for 5-alpha-dihydrotestosterone, testosterone, & 17-beta-estradiol
- regulates plasma metabolic clearance rate of steroid hormones by controlling their plasma concentration
- testosterone is transported in circulation bound to SHBG*.
- only 1-3% of testosterone is free (active form)
* non-specific binding of testosterone to albumin occurs
Structure: contains 2 laminin G-like domains
Compartment:
- secreted (putative)
- in testis, it is synthesized by the Sertoli cells, secreted into the lumen of the seminiferous tubule & transported to the epididymis
Alternative splicing:
- named isoforms=2;
- additional isoforms seem to exist
Expression:
- isoforms 1 & 2 are present in liver & testis
- in testis, it is synthesized by the Sertoli cells
- expression may be inhibited by insulin & prolactin [5]
Pathology:
1) increased serum SHBG levels
a) hyperthyroidism
b) hyperestrogenic states
1] pregnancy
2] oral contraceptives
3] gynecomastia
2) decreased serum SHBG
a) insulin resistance
b) increased risk of type-2 diabetes [3]
Related
sex hormone-binding globulin (SHBG) in serum
General
globulin
glycoprotein
plasma protein
Properties
SIZE: entity length = 402 aa
MW = 44 kD
COMPARTMENT: plasma
MOTIF: signal sequence {1-29}
Thr glycosylation site {T36}
Laminin G-like 1 {45-217}
MOTIF: cysteine residue {C193}
MODIFICATION: cysteine residue {C217}
cysteine residue {C217}
MODIFICATION: cysteine residue {C193}
Laminin G-like 2 {224-390}
MOTIF: cysteine residue {C362}
MODIFICATION: cysteine residue {C390}
N-glycosylation site {N380}
cysteine residue {C390}
MODIFICATION: cysteine residue {C362}
N-glycosylation site {N396}
Database Correlations
OMIM 182205
UniProt P04278
Pfam PF00054
Entrez Gene 6462
Kegg hsa:6462
References
- UniProt :accession P04278
- ABC's of Interptretive Laboratory Data, 4th ed, Bakerman S et al
(eds), Interpretive Laboratory Data Inc, Scottsdale, AZ, 2003
http://www.bakermanbooks.com
- Ding EL et al
Sex hormone-binding globulin and risk of type 2 diabetes
in women and men.
N Engl J Med 2009 Sep 17; 361:1152.
PMID: 19657112
- Wikipedia; androgen-binding protein entry
http://en.wikipedia.org/wiki/androgen-binding_protein
- Plymate SR, Matej LA, Jones RE, Friedl KE.
Inhibition of sex hormone-binding globulin production in the
human hepatoma (Hep G2) cell line by insulin and prolactin.
J Clin Endocrinol Metab. 1988 Sep;67(3):460-4.
PMID: 2842359