Gallichrome
Source Gallichrome at Peptiology
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Summary
Gallichrome is a gallium(III) analogue of the microbial siderophore ferrichrome, a cyclic hexapeptide that chelates metal ions. In research, it serves as a stable, diamagnetic surrogate for ferrichrome, allowing detailed structural and biophysical studies of bacterial iron‑uptake proteins such as the periplasmic binding protein FhuD.
Mechanism of Action
Gallichrome mimics ferrichrome by presenting three hydroxamate groups that coordinate the Ga³⁺ ion. In the periplasmic binding protein FhuD, the metal‑hydroxamate complex fits into a shallow pocket lined with aromatic residues; Arg and Tyr side chains form hydrogen bonds and electrostatic contacts with the hydroxamate moieties, stabilising the ligand‑protein complex. The rigid cyclohexapeptide backbone provides a defined scaffold for these interactions, enabling the protein to discriminate bound versus unbound states.
What the Research Shows
Three peer‑reviewed studies have examined gallichrome. A 1990 NMR investigation characterised the solution conformations of gallichrome and its aluminium analogue, showing that the metal‑bound peptide adopts a rigid structure comparable to ferrichrome and that the free peptide displays multiple conformers in DMSO. In 2000, X‑ray crystallography of Escherichia coli FhuD complexed with gallichrome revealed a novel protein fold and detailed contacts between the ligand and aromatic residues in the binding pocket. A 2005 molecular‑dynamics simulation of FhuD without its siderophore suggested modest domain motions that could allow the inner‑membrane transporter FhuB to distinguish bound from unbound protein. Collectively, the evidence is limited to in‑vitro structural and computational work.
Reported Benefits
Gallichrome provides a diamagnetic, stable proxy for ferrichrome, facilitating high‑resolution NMR and crystallographic studies that would be difficult with the paramagnetic iron complex. Its use has elucidated the architecture of siderophore‑binding proteins, informed models of bacterial iron acquisition, and may guide the design of novel antimicrobial agents targeting siderophore pathways.
Limitations of the Evidence
All data derive from in‑vitro or computational experiments; no functional assays, bacterial uptake studies, or animal models have evaluated gallichrome’s biological activity. Consequently, its relevance to physiological iron transport or therapeutic applications remains speculative. Additionally, the limited number of studies restricts confidence in broader conclusions about its behavior in diverse bacterial species.
Safety Considerations
The published literature provides no toxicological or pharmacological data for gallichrome in humans or animals. As a gallium‑containing compound, it could exhibit metal‑related toxicity if ingested or inhaled, but such effects have not been documented. In laboratory settings it is handled as a chemical reagent dissolved in organic solvents (e.g., DMSO) under standard safety protocols, including protective equipment and proper waste disposal.
How It Is Administered
Gallichrome is employed as a dissolved reagent for biochemical assays, NMR spectroscopy, and crystallography. Typical preparations involve dissolving the solid in dimethyl‑sulfoxide (DMSO) or aqueous buffers at micromolar concentrations. It is not formulated for systemic administration and has no approved clinical route of delivery.
Routes of Administration
No administration routes recorded yet.
Goals & Uses
No goal associations recorded yet.
Contraindications
No contraindications recorded yet.
Adverse Effects
No adverse effects recorded yet.
Drug Interactions
No drug interactions recorded yet.
Population Constraints
No population constraints recorded yet.
Regulatory Status
No regulatory status recorded yet.
Evidence & Sources
- Journal ArticleLowKrewulak KD, Shepherd CM, Vogel HJ2005-01-01T00:00:00.000000Z
- Journal ArticleLowConstantine KL, et al.1990-01-01T00:00:00.000000Z
- Journal ArticleLowClarke TE, et al.2000-01-01T00:00:00.000000Z
Frequently Asked Questions
What type of compound is gallichrome?
Gallichrome is a synthetic gallium(III) analogue of the siderophore ferrichrome. It is a cyclic hexapeptide that chelates a metal ion, used primarily as a research tool to study iron‑binding proteins.
Is gallichrome used as a drug or therapeutic agent?
No. The available studies describe gallichrome only in structural and biophysical experiments; there is no evidence of clinical testing, regulatory approval, or therapeutic use.
How is gallichrome typically handled in the laboratory?
Researchers dissolve gallichrome in solvents such as dimethyl‑sulfoxide (DMSO) to create solutions for NMR spectroscopy or crystallization trials. Standard chemical safety measures—gloves, goggles, and fume‑hood work—are recommended.
Can gallichrome replace ferrichrome in bacterial iron uptake studies?
Gallichrome mimics ferrichrome’s geometry and metal‑hydroxamate coordination, allowing it to bind the same protein pockets in vitro. However, functional studies of bacterial iron transport using gallichrome have not been reported.
Are there any known safety concerns with gallichrome?
Published data do not include toxicity assessments. As a gallium‑based compound, it could be hazardous if mishandled, so laboratory safety protocols should be followed, but no specific adverse effects have been documented.
What is Gallichrome?
Gallichrome is a gallium(III) analogue of the microbial siderophore ferrichrome, a cyclic hexapeptide that chelates metal ions. In research, it serves as a stable, diamagnetic surrogate for ferrichrome, allowing detailed structural and biophysical studies of bacterial iron‑uptake proteins such as the periplasmic binding protein FhuD.