GHK-Cu (Copper Tripeptide-1)
GHK-Cu is the copper(II) coordination complex of the tripeptide glycyl-L-histidyl-L-lysine (GHK), a naturally occurring sequence first isolated from human plasma. It is studied in vitro as a low-molecular-weight copper-binding ligand and a model system for peptide-metal coordination and extracellular-matrix research.
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GHK-Cu is a metallopeptide formed when the tripeptide glycyl-L-histidyl-L-lysine (sequence Gly-His-Lys; H-Gly-His-Lys-OH) chelates a divalent copper ion, Cu(II). The free tripeptide (GHK) has the molecular formula C14H24N6O4 and a molecular weight of approximately 340.39 g/mol; coordination of one Cu(II) ion yields the 1:1 complex, commonly written C14H22CuN6O4. The peptide ligand presents an N-terminal glycine amine, the imidazole nitrogen of the central histidine residue, and a deprotonated peptide-bond nitrogen as principal donor atoms, giving a well-characterized square-planar coordination geometry around copper that has made GHK-Cu a frequently cited reference system in bioinorganic and coordination chemistry. The compound is also catalogued under the names copper tripeptide-1 and prezatide copper (as the acetate salt). In its uncomplexed form GHK is a small, water-soluble basic tripeptide bearing the imidazole and ε-amino side chains of histidine and lysine.
Mechanism (in-vitro research context)
In in-vitro systems, GHK-Cu is characterized primarily by its metal-coordination behavior: the GHK ligand binds Cu(II) with high affinity, and the resulting complex serves as a defined copper donor/acceptor species in studies of copper exchange, redox equilibria, and metal trafficking at the cellular level. The donor-atom set (terminal amine, imidazole nitrogen, and an amide nitrogen) and the associated stability constants are used as a model for plasma copper coordination. Research framing also addresses interactions of GHK and GHK-Cu with extracellular-matrix proteins and matrix-remodeling enzyme systems in cultured cells and cell-free assays, and the use of the peptide as a chelating scaffold for examining metalloprotein chemistry. Reported activity is described at the level of receptor-independent metal-ligand coordination and gene-expression profiling in cultured fibroblasts; no in-vivo or therapeutic mechanism is implied here.
Research areas
- Peptide–copper(II) coordination chemistry and stability-constant determination in cell-free systems
- Extracellular-matrix and collagen-synthesis assays in cultured fibroblasts
- Copper homeostasis and trace-metal exchange studies in cell culture
- Metalloprotein and bioinorganic model-complex characterization (EPR, UV-Vis, potentiometry)
- Transcriptomic / gene-expression profiling of cultured cells exposed to the complex
- Redox and radical-scavenging chemistry of the copper(II) center in cell-free systems
Chemistry
- Molecular weight
- 340.39 g/mol (free GHK tripeptide, C14H24N6O4); ~401.9 g/mol for the 1:1 Cu(II) complex C14H22CuN6O4
- CAS
- 89030-95-5 (GHK-Cu complex); 49557-75-7 (free GHK tripeptide)
- Formula
- C14H24N6O4 (free GHK); C14H22CuN6O4 (GHK-Cu copper complex)
- Sequence
- Gly-His-Lys (glycyl-L-histidyl-L-lysine); H-Gly-His-Lys-OH
Laboratory handling
For laboratory use, GHK and GHK-Cu are typically supplied as lyophilized solids and stored desiccated at -20 C, protected from light and moisture, where the solid is stable for extended periods. Stock solutions are commonly prepared in water or aqueous buffer; because the copper(II) center is redox-active, freshly prepared solutions are preferred and repeated freeze-thaw cycles should be minimized to limit oxidation and metal-ligand dissociation. Solution speciation is pH-dependent, so buffer composition and pH should be controlled and recorded for reproducible coordination behavior. Identity and purity are generally assessed by reversed-phase HPLC and mass spectrometry, with copper content confirmable by ICP-MS or UV-Vis spectrophotometry. All handling described here is for analytical and in-vitro laboratory research only.
FAQ
What is the amino acid sequence?
The peptide ligand is the tripeptide glycyl-L-histidyl-L-lysine, sequence Gly-His-Lys (H-Gly-His-Lys-OH). In GHK-Cu this tripeptide is coordinated to a single Cu(II) ion.
What is the difference between GHK and GHK-Cu?
GHK is the free tripeptide (C14H24N6O4, MW ~340.39). GHK-Cu is its 1:1 copper(II) coordination complex (C14H22CuN6O4), in which the terminal amine, histidine imidazole, and an amide nitrogen serve as donor atoms to the copper center.
How is purity verified?
Purity of the peptide is typically determined by reversed-phase HPLC with UV detection, and identity is confirmed by mass spectrometry (ESI-MS or MALDI-TOF). For the copper complex, copper stoichiometry can be additionally checked by ICP-MS or UV-Vis spectrophotometry of the characteristic d-d absorption band.
How should it be stored in the lab?
Store the lyophilized solid desiccated at -20 C, protected from light. Prepare aqueous stock solutions fresh when possible, control buffer pH, and minimize freeze-thaw cycles to limit oxidation of the redox-active copper center and metal-ligand dissociation.
What analytical techniques characterize the copper coordination?
Common cell-free characterization methods include UV-Vis spectroscopy (d-d and charge-transfer bands), electron paramagnetic resonance (EPR) for the Cu(II) coordination environment, and potentiometric titration for determining stability constants and pH-dependent speciation.
References
- Pickart L, Thaler MM. Tripeptide in human serum which prolongs survival of normal liver cells and stimulates growth in neoplastic liver. Nature New Biology, 1973;243(124):85-87.
- Schlesinger DH, Pickart L, Thaler MM. Growth-modulating serum tripeptide is glycyl-histidyl-lysine. Experientia, 1977;33(3):324-325.
- Pickart L, Freedman JH, Loker WJ, et al. Growth-modulating plasma tripeptide may function by facilitating copper uptake into cells. Nature, 1980;288(5792):715-717.
- Maquart FX, Pickart L, Laurent M, et al. Stimulation of collagen synthesis in fibroblast cultures by the tripeptide-copper complex glycyl-L-histidyl-L-lysine-Cu2+. FEBS Letters, 1988;238(2):343-346.
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