Signal patches are one of two identified signalling mechanisms by which proteins are distributed to the correct locations following their synthesis. Signal patches comprise a specific three-dimensional arrangement on the surface of a folded protein; the same way as the active sites of complex enzymes form. Unlike the situation with signal peptides, amino acid residues comprising a signal patch do not have to be contiguous along the polypeptide chains, and they generally remain part of the final functional protein. Because they result from the complex three- dimensional protein-folding pattern these sorting signals are difficult to identify precisely, and thus pose difficulties during experimentation.

As an example, newly synthesised lysosomal proteins are able to target the lysosomes from the Golgi apparatus using a signal patch.