Nucleating scaffold proteins

Recent interest has focused on acidic phosphoproteins, such as bone sialoprotein, acting as sites of nucleation. These proteins contain motifs (eg, poly-Asp and poly-Glu stretches) that bind calcium and may provide an initial scaffold for mineralization. Some macromolecules, such as certain proteoglycans and glycoproteins, can also act as inhibitors of nucleation. 

Figure 5. A working model for [2Fe-2S] formation on the ISU scaffold that is consistent with published data. (A) Frataxin mediates initial delivery of iron ions to apo ISU through an iron-bridged complex, establishing a nucleation site for [2Fe 2S] cluster formation. (B) Subsequent sulfide delivery is mediated through the persulfide form of NifS/IscS that forms a complex with ISU. Reductive cleavage of NifS/IscS persulfide bonds by reduced NFU yields the two equivalents of inorganic S for cluster formation. The reduced [2Fe 2S] cluster initially formed on IscU may then be oxidized by F

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