The secretory signal peptide is a ubiquitous protein- sorting signal that targets its passenger protein for translocation across the endoplasmic reticulum membrane in eukaryotes and the cytoplasmic membrane in prokaryotes.

After synthesis, all proteins need to be properly sorted to reach their correct locations in the cell. The subcellular localization of proteins can be determined by various experimental techniques such as those employed within the Cell Profiling Unit at SciLifeLab but can also be predicted by computational means. One of the most highly used programs in this area is SignalP. The first version of SignalP was published already in 1997. The latest version, SignalP4.0, has just been published in Nature Methods as a result of a collaboration between scientists at SciLifeLab and the Center for Biological Sequence Analysis at the Technical University of Denmark.