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The groove between the alpha- and beta-subunits of hormones with lutropin (LH) activity appears to contact the LH receptor, and its conformation is changed during hormone binding.
- Source :
-
The Journal of biological chemistry [J Biol Chem] 1995 Aug 25; Vol. 270 (34), pp. 20011-9. - Publication Year :
- 1995
-
Abstract
- Gonadotropins are heterodimeric glycoprotein hormones that control vertebrate fertility through their actions on gonadal lutropin (luteinizing hormone, LH) and follitropin (follicle-stimulating hormone, FSH) receptors. The beta-subunits of these hormones control receptor binding specificity; however, the region of the beta-subunit that contacts the receptor has not been identified. By a process of elimination we show this contact to be the portions of beta-subunit loops one and three found in a hormone groove created by the juxtaposition of the alpha- and beta-subunits. Most other regions of the beta-subunit can be recognized by antibodies that bind to human chorionic hormone (hCG)-receptor complexes or replaced without disrupting hormone function. Using a series of bovine LH/hCG and human FSH/hCG beta-subunit chimeras we identified key hCG beta-subunit residues in the epitopes of two antibodies that bind to hCG-receptor complexes. These epitopes include the surfaces of beta-subunit loops one and three near residue 74 on the outside of the hormone groove and parts of the C-terminal end of the "seat belt" that holds the two subunits together. The antibody that recognized residue 74 bound to receptor complexes containing most mammalian lutropins better than to the free hormones, an indication that the outside surface of the beta-subunit groove is altered during hormone binding. This region of the beta-subunit is furthest from the alpha-subunit and is recognized equally well in the free beta-subunit and in the heterodimer. Thus, the receptor associated increase in antibody binding appears due to an interaction of this portion of the beta-subunit with the receptor and not to an effect of the receptor on the relative positions of the alpha- and beta-subunits. Unlike most previous studies designed to identify portions of the beta-subunit likely to contact the LH receptor, this indirect approach provides data that are more easily interpreted because it does not rely on the use of mutations that disrupt hormone function. The approach described here should be valuable for studying the receptor interactions of other complex ligands.
- Subjects :
- Amino Acid Sequence
Animals
Base Sequence
Binding Sites
Chorionic Gonadotropin chemistry
Chorionic Gonadotropin genetics
Chorionic Gonadotropin metabolism
Conserved Sequence
DNA Primers genetics
Epitope Mapping
Follicle Stimulating Hormone chemistry
Follicle Stimulating Hormone genetics
Follicle Stimulating Hormone metabolism
Humans
Luteinizing Hormone genetics
Models, Molecular
Molecular Sequence Data
Protein Conformation
Protein Folding
Recombinant Fusion Proteins chemistry
Recombinant Fusion Proteins genetics
Recombinant Fusion Proteins metabolism
Luteinizing Hormone chemistry
Luteinizing Hormone metabolism
Receptors, LH metabolism
Subjects
Details
- Language :
- English
- ISSN :
- 0021-9258
- Volume :
- 270
- Issue :
- 34
- Database :
- MEDLINE
- Journal :
- The Journal of biological chemistry
- Publication Type :
- Academic Journal
- Accession number :
- 7650019
- Full Text :
- https://doi.org/10.1074/jbc.270.34.20011