Key findings
- The crystal structure showed both subunits folded with three disulphide bonds forming a cystine knot, and the heterodimer held together by a beta-subunit segment that wraps the alpha-subunit and is fastened by the Cys26 to Cys110 disulphide. [1]
- A 2.6 angstrom structure of partially deglycosylated recombinant protein found the O-linked sugar rich carboxy-terminal peptide of the beta-subunit disordered, and an extensive interface carrying two inter-chain beta-sheets. [2]
- Mass spectrometry of one recombinant preparation detected more than 30 glycoforms of the alpha-subunit alone and distinguished three batches of the same product. [3]
- A workflow across ten lots and brands identified about 1000 intact N- and O-linked glycopeptides, of which 167 differed significantly between naturally derived and recombinant material. [4]
Identity and structure
- Architecture
- A heterodimer of two different subunits, each with a cystine knot at the core of extended hairpin loops [1][2]
- Subunit interface
- A beta-subunit segment wraps the alpha-subunit and is covalently fastened by the Cys26 to Cys110 disulphide, a feature the authors call essential for association and for receptor binding [1]
- Glycosylation
- The shared alpha-subunit carries two N-glycosylation sites, and more than 30 alpha-subunit glycoforms were detected in a single recombinant preparation [3]
- Source dependence
- Glycopeptide profiles differ measurably between naturally derived and recombinant preparations of the same nominal protein [4]
- Form as supplied
- Sterile lyophilized powder; the catalog name carries an activity figure rather than a mass
Mechanism as studied
The structural work places the segments implicated in receptor binding together on one side of the molecule, with a glycosylation site implicated in signal transduction but not in binding nearby. The authors suggest that arrangement may couple ligand binding to signaling. [2]
Single-molecule force spectroscopy resolved two binding mechanisms within the receptor extracellular domain, one at the hinge loop and one at the leucine rich repeats, and the same dual mode appeared with full-length receptor on the membranes of living cells. Mutagenesis of the hinge region separately showed that the hormone and its pituitary counterpart engage that region differently. [5][6]
Research findings
Structural
- System
- Crystallographic analysis of the human heterodimer
- Measured
- Topology of each subunit, disulphide connectivity, organisation of the heterodimer interface
- Reported
- Each subunit has a similar topology with three disulphide bonds forming a cystine knot, the same folding motif found in some protein growth factors. A beta-subunit segment wraps the alpha-subunit and is covalently linked by the Cys26 to Cys110 disulphide, which the authors call essential both for heterodimer association and for receptor binding by the glycoprotein hormones. [1]
Structural
- System
- Recombinant selenomethionyl protein produced in mammalian cells, partially deglycosylated and solved at 2.6 angstrom by multiwavelength anomalous diffraction
- Measured
- Tertiary fold of each subunit, subunit interface, order of the beta-subunit carboxy-terminal peptide, position of the receptor binding segments
- Reported
- Despite only 10 percent sequence identity the two subunits share a similar tertiary fold, each with a cystine knot at its core. The interface carries two inter-chain beta-sheets and a disulfide tethered arm from the beta-subunit. The O-linked sugar rich carboxy-terminal peptide of the beta-subunit is disordered. Segments implicated in receptor binding sit together on one side of the molecule. [2]
In vitro
- System
- Single-molecule force spectroscopy between the glycoprotein and separated receptor domains, then full-length receptor on the membranes of living cells, with molecular dynamics simulations
- Measured
- Binding mechanisms and lifetimes at the hinge loop and at the leucine rich repeats, and the dissociation pathway
- Reported
- Two distinct binding mechanisms were detected in the receptor extracellular domain. The leucine rich repeat interaction showed a bimodal energy landscape with an outer barrier lifetime of 18.4 s against 0.67 s for the hinge loop. The same dual mode appeared with full-length receptor on cell membranes. Simulations described a sequential three-step dissociation in which electrostatic forces repeatedly favour the hinge loop interaction. [5]
In vitro
- System
- A homology model of the hormone receptor complex followed by characterisation of hinge region fragments and by block-wise polyalanine and double-proline mutants of the receptor
- Measured
- Signaling at wild type and mutant receptors for the placental hormone and for its pituitary counterpart
- Reported
- Helix preserving changes did not alter signaling by either hormone. The structure-disturbing Q303P and E305P double mutant reduced signaling by the placental hormone but not by the pituitary one, the opposite of the effect reported for exon10 deletion. The authors place the difference in the L2-beta loop of the hormones and in the hinge region of the receptor. [6]
Analytical
- System
- A recombinant preparation analysed at the intact level by nano reversed phase liquid chromatography coupled to Orbitrap high resolution mass spectrometry, with three batches compared
- Measured
- Number of alpha-subunit glycoforms, retention time and peak area repeatability, batch to batch comparison
- Reported
- More than 30 alpha-subunit glycoforms were detected without overlapping isotopic patterns, including minority isoforms. Retention time relative standard deviations averaged 0.4 percent and peak area values averaged 16 percent, which allowed semi-relative quantification. Three batches of the same product were compared qualitatively and semi-quantitatively. [3]
Analytical
- System
- Ten different lots and brands of commercial material, tryptically digested, labeled with tandem mass tags and analysed by high resolution liquid chromatography mass spectrometry with alternating dissociation methods
- Measured
- Site-specific location, identification and relative quantification of N- and O-linked glycosylation across the lots
- Reported
- About 1000 intact N- and O-linked glycopeptides were identified from the digested material. Partial least squares discriminant analysis found 167 glycopeptides that differed significantly between naturally derived and recombinant preparations. The authors present the method as suitable for similarity assessment and counterfeit identification. [4]
Handling for in-vitro work
- Identity checks in cited work
- Tryptic digestion with tandem mass tag labeling distinguished lots and brands of the same nominal product in one analytical run [4]
- Storage
- Lyophilized material kept at minus 20 degrees C, dark and dry; reconstituted aliquots kept cold and used promptly
Open questions
- No cited study converts an activity figure into a mass for a given preparation, so the relationship between the two rests on a material specific potency assignment that this set does not supply.
- The cited structures used recombinant, partially deglycosylated protein, so the fully glycosylated material a listing supplies is not the exact species whose coordinates were solved.
A large clinical literature exists for this glycoprotein and concerns finished pharmaceutical preparations. It is out of scope for a research material profile and none of it is summarized here.
Lot records
Check the record for the exact material you order. A published paper and a batch certificate answer different questions.
No published lot is available for this exact compound name.
Read a certificate of analysis ↗References
- Lapthorn AJ, Harris DC, Littlejohn A, et al. Crystal structure of human chorionic gonadotropin. Nature. 1994.
- Wu H, Lustbader JW, Liu Y, et al. Structure of human chorionic gonadotropin at 2.6 A resolution from MAD analysis of the selenomethionyl protein. Structure (London, England : 1993). 1994.
- Al Matari A, Combès A, Camperi J, et al. Identification and semi-relative quantification of intact glycoforms by nano-LC-(Orbitrap)MS: application to the α-subunit of human chorionic gonadotropin and follicle-stimulating hormone. Analytical and bioanalytical chemistry. 2020.
- Zhu H, Qiu C, Ruth AC, et al. A LC-MS All-in-One Workflow for Site-Specific Location, Identification and Quantification of N-/O- Glycosylation in Human Chorionic Gonadotropin Drug Products. The AAPS journal. 2017.
- Han Q, He Y, Yao Z, et al. Single-molecule force spectroscopy discovers a dual-binding mode in the hCG-mediated activation of LHCGR. Protein science : a publication of the Protein Society. 2026.
- Grzesik P, Kreuchwig A, Rutz C, et al. Differences in Signal Activation by LH and hCG are Mediated by the LH/CG Receptor's Extracellular Hinge Region. Frontiers in endocrinology. 2015.
Publication records fetched from PubMed on 2026-09-20. Profile text reviewed 2026-09-20.