Scaffolds localize the signaling reaction to a specific area in the cell, a process that could be important for the local production of signaling intermediates.  A particular example of this process is the scaffold, A-kinase anchor proteins (AKAPs), which target cyclic AMP-dependent protein kinase (PKA) to various sites in the cell.  This localization is able to locally regulate PKA and results in the local phosphorylation by PKA of its substrates.