Inhibition of iodine-125-labeled human follitropin binding to testicular receptor by epidermal growth factor and synthetic peptides
Two tetrapeptide sequence homologies between mouse epidermal growth factor precursor (mEGFP) and human follitropin (FSH) were revealed by a computer program that identifies identical residues among polypeptide sequences. The two tetrapeptides, Lys-Thr-Cys-Thr (KTCT) and Thr-Arg-Asp-Leu (TRDL), are present in the hormone-specific beta subunit of FSH from all species studied. These tetrapeptides are not present in the alpha subunit, which is common to all pituitary glycoprotein hormones. Both tetrapeptides are also found in mEGFP, and one tetrapeptide, TRDL, is located within the 53-residue form of mEGF purified from mouse submaxillary glands. Computer-generated hydropathy profiles predicted that both tetrapeptides are located in hydrophilic portions of the FSH beta subunit and that TRDL is in a hydrophilic portion of commercially available mEGF. Therefore, the tetrapeptides might be accessible to receptor binding sites for FSH. We report that mEGF inhibits binding of /sup 125/I-labeled human FSH to receptors in testis by 50% (I50) at a concentration of 1.8 X 10(-5) M. No binding inhibition was observed by GnRH or arginine-vasopressin at 10(-4) M, neither of which contain the tetrapeptide sequences. FSH beta subunit, which contains both tetrapeptides, also inhibited binding (I50 = 9 X 10(-8) M) of /sup 125/I-labeled human FSH to testis receptor. Thus, it appears that FSH beta subunit and mEGF are capable of inhibiting binding of FSH to testicular FSH receptors, presumably through interactions that include the homologous tetrapeptides. This presumption was supported by the observation that the synthetic tetrapeptides (KTCT or TRDL) were also active in inhibiting binding of /sup 125/I-labeled human FSH to testis receptor.
- OSTI ID:
- 5097886
- Journal Information:
- Biochemistry; (United States), Vol. 9
- Country of Publication:
- United States
- Language:
- English
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FSH
RECEPTORS
AMINO ACID SEQUENCE
BIOCHEMICAL REACTION KINETICS
CATTLE
CHEMICAL BONDS
INHIBITION
IODINE 125
LABELLED COMPOUNDS
PEPTIDES
TRACER TECHNIQUES
ANIMALS
BETA DECAY RADIOISOTOPES
DAYS LIVING RADIOISOTOPES
DOMESTIC ANIMALS
ELECTRON CAPTURE RADIOISOTOPES
GONADOTROPINS
HORMONES
INTERMEDIATE MASS NUCLEI
IODINE ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
MAMMALS
MEMBRANE PROTEINS
MOLECULAR STRUCTURE
NUCLEI
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
PEPTIDE HORMONES
PITUITARY HORMONES
PROTEINS
RADIOISOTOPES
REACTION KINETICS
RUMINANTS
VERTEBRATES
550201* - Biochemistry- Tracer Techniques