Interprotein cluster transfer

One approach for identifying the type of iron center in a protein has been to remove the center, intact, by ligand exchange between the protein and an exogenous acceptor ligand (reviewed by Berg and Holm, 1982). The removed, or extruded, center is identified by comparison of its spectral properties (usually absorption spectrum) to known model compounds. Alternatively, the extruded center can be inserted into a second apoprotein which has been previously determined to accept only one type of iron center. The reconstructed standard protein is then analyzed by EPR. The latter method, interprotein cluster transfer, requires that acceptor apoproteins for all known classes of centers are included in the reaction mixture and that the reconstituted reporter ... 

The electron-transfer P-cluster and the catalytic FeMo-cofactor of the MoFe-protein of nitrogenase have been assembled only by biosynthesis. Whereas the P-cluster most likely participates in interprotein electron transfer, the FeMo-cofactor is the active site of substrate binding and reduction [43-46,48-51]. 

Fig. 9 A) Time dependent MALDI MS data of growth of luminescent gold quantum clusters Au25 in the protein lactotransferrin indicating the emergence of free protein and interprotein metal ion transfer. B) XPS spectra showing the presence of Au state before the addition of NaOH and Au(0) after the addition of NaOH (adapted from Ref. 239).

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