SNAP-25 is also an iron–sulfur protein

SNAP-25 has a cysteine cluster located at its linker domain. In vivo, the cysteine residues in this cluster can be palmitoylated, and the hydrophobic palmitate molecules can target SNAP-25 to the presynaptic membrane. Here, we report that the SNAP-25a expressed in Escherichia coli is also an iron–sulfur protein binding an iron–sulfur cluster using the cysteine residues in its cysteine cluster. Therefore, SNAP-25a uses the same cysteine residues to bind two different prosthetic groups (iron–sulfur cluster and palmitate). Because the binding sites of these two prosthetic groups overlap, we suggest that these two modifications occur at different times, and probably at different places in the cell.