FERREDOXIN AND FERREDOXIN-HEME MAQUETTES

A 16-amino acid residue peptide derived from a consensus motif of natu ral ferredoxins incorporates a tetranuclear iron sulfur cluster under physiological conditions, Successful assembly of the [4FE-4S](2+/1+) c luster within a monomeric peptide was demonstrated using size exclusio n chromatography, UV-visible, visible CD, and cryogenic EPR spectrosco pies. The robustness of [4Fe-4S](2+/1+) formation was tested using pep tides with either the ligating cysteine exchanged for alanine or with the intervening amino acids replaced by glycine, The small size of the peptide allows for modular incorporation into more complex protein st ructures. In one larger structure, we describe a tetra-cu-helix bundle that self-assembles both iron-sulfur clusters and hemes, thereby demo nstrating feasibility for the general synthesis of maquettes containin g multiple, juxtaposed redox cofactors, This is a motif common to the catalytic sites of native oxidoreductases.