Ferrichrome

Ferrichrome is a cyclic hexapeptide composed of three glycine and three modified ornithine residues that bind Fe(III) with hydroxamate groups [-N(OH)C(=O)C-]. Ferrichrome, first isolated in 1952, has been found to be produced by fungi of the genera Aspergillus, Ustilago, and Penicillium.

ferrichrome diagram


button Show central Fe and nearest neighbors: 6 O

This model shows the near-perfect octahedral coordination of the central Fe atom, with six oxygens as the apices of the octahedron. The symmetry of the central Fe atom with its nearest neighbors is one of the key factors in chelate stability.

In spacefilling mode, this model show that the central Fe atom is nearly completely concealed by coordinating oxygens and nitrogens. No coordination by additional water (H2O) or hydroxide (OH-) is permitted in this structure, which adds to the stability of this chelate.

button Show cyclic hexapeptide backbone

button Show hydroxamate groups

Identify the six amino acids in the hexapeptide!

button ornithine(1), Nd-acetyl-Nd-hydroxy-L-
button ornithine(2),       " "
button ornithine(3),       " "
button glycine(1) (NH2CH2COOH)
button glycine(2)
button glycine(3)

button Show all


References:

D. van der Helm, JR Baker, DL Eng-Wilmot, MB Hossain, and RA Loghry. 1980. Crystal structure of ferrichrome and a comparison with the structure of ferrichrome A. J. Am Chem. Soc. 102:4224-4231.