Association/dissociation of gonadotropin subunits involves disulfide bridge disruption which is influenced by carbohydrate moiety

The association and dissociation rates of pituitary porcine luteinizing hormone (pLH) and equine LH (eLH) at oxidizing potential were slow and those of equine choriogonadotropin (eCG) were even much slower. At reducing potential mimicking endoplasmic reticulum condition, association of pLH subunits...

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Bibliographic Details
Published in:Biochemical and biophysical research communications 2004-11, Vol.324 (2), p.868-873
Main Authors: Galet, Colette, Lecompte, François, Combarnous, Yves
Format: Article
Language:English
Subjects:
Animals
Carbohydrates - chemistry
Choriogonadotropin
Chorionic Gonadotropin - chemistry
Disulfide bridge
Disulfides - chemistry
Gonadotropins - chemistry
Horses
Hot Temperature
Kinetics
Luteinizing hormone
Luteinizing Hormone - chemistry
Lutropin
Oxidation-Reduction
Oxygen - metabolism
Pituitary Gland - metabolism
Protein Binding
Protein Structure, Quaternary
Quaternary structure
Receptor binding
Recombination, Genetic
Structure-Activity Relationship
Structure–Activity
Swine
Temperature
Thiocyanates - pharmacology
Time Factors
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Summary:The association and dissociation rates of pituitary porcine luteinizing hormone (pLH) and equine LH (eLH) at oxidizing potential were slow and those of equine choriogonadotropin (eCG) were even much slower. At reducing potential mimicking endoplasmic reticulum condition, association of pLH subunits was observed in less than 5min instead of 24h at oxidizing potential. At neutral pH and 37°C, DTNB and 2-nitro-5-thiocyanobenzoic acid (NTCB) were found to react with two cysteine residues (i.e., one S–S bridge) in pLH. The temperature dependence of the NTCB reaction on pLH was found to be similar to that of the dissociation of the hormone (Tm∼75°C). The tight correlation between the reaction of two cysteines and dissociation of the subunits of pLH and eLH strongly suggests that transient opening of one fragile disulfide bridge is required for heterodimer assembly. Moreover, the absence of cysteine reaction with eCG indicates that its bulky carbohydrate chains exert a negative influence on the opening of this bridge leading to considerably diminished association–dissociation rates of its subunits.
ISSN:0006-291X
1090-2104
DOI:10.1016/j.bbrc.2004.09.143