What's signal peptide?
A signal peptide, sometimes referred to as signal sequence, targeting signal, localization signal, localization sequence, transit peptide, leader sequenceor leader peptide. It is a short peptide, usually 16-30 amino acids long.  It present at the N-terminus of the majority of newly synthesized proteins that are destined towards the secretory pathway.  These proteins include those that reside either inside certain organelles (the endoplasmic reticulum, golgi or endosomes), secreted from the cell, or inserted into most cellular membranes. Although most type I membrane-bound proteins have signal peptides, the majority of type II and multi-spanning membrane-bound proteins are targeted to the secretory pathway by their first transmembrane domain, which biochemically resembles a signal sequence except that it is not cleaved.
The properties of the amino acids that constitute the signal peptide region of a protein are the significant factors determining interaction with the protein transport system, hence the destination to which that protein is delivered. Different classes of signal peptide are used to specify different cellular placement. It should be reiterated that not all proteins possess signalling regions; those which don’t are maintained in the cytoplasm.
Function (Translocation) of Signal peptides
Signal peptides function to prompt a cell to translocate the protein, usually to the cellular membrane. In prokaryotes, signal peptides direct the newly synthesized protein to the SecYEG protein-conducting channel, which is present in the plasma membrane. A homologous system exists in eukaryotes, where the signal peptide directs the newly synthesized protein to the Sec61 channel, which shares structural and sequence homology with SecYEG, but is present in the endoplasmic reticulum. Both the SecYEG and Sec61 channels are commonly referred to as the translocon, and transit through this channel is known as translocation. While secreted proteins are threaded through the channel, transmembrane domains may diffuse across a lateral gate in the translocon to partition into the surrounding membrane.
Signal peptides are extremely heterogeneous and many prokaryotic and eukaryotic signal peptides are functionally interchangeable even between different species however the efficiency of protein secretion is strongly determined by the signal peptide.
Please note that all peptides in GiantLab.net online store are only for laboratory research purpose, not for human consumption. If you have any questions or inquiry, please feel free to contact the knowledgeable and experienced Giant Lab team: firstname.lastname@example.org & email@example.com.
- Kapp, Katja; Schrempf, Sabrina; Lemberg, Marius K.; Dobberstein, Bernhard (2013-01-01). Post-Targeting Functions of Signal Peptides. Landes Bioscience.
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