Editing Signal peptide (section)

{{Short description|Short peptide present at N-terminal of newly synthesized proteins}}
{{Infobox protein family
| Symbol = N/A
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| OPM family = 256
| OPM protein = 1skh
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| CDD =
}}
A '''signal  peptide''' (sometimes referred to as '''signal sequence''', '''targeting signal''', '''localization signal''', '''localization sequence''', '''transit peptide''', '''leader sequence''' or '''leader peptide''') is a short [[peptide]] (usually 16–30 [[amino acid]]s long)<ref>{{Cite book|url=https://www.ncbi.nlm.nih.gov/books/NBK6322/|title=Post-Targeting Functions of Signal Peptides|last1=Kapp|first1=Katja|last2=Schrempf|first2=Sabrina|last3=Lemberg|first3=Marius K.|last4=Dobberstein|first4=Bernhard|date=2013-01-01|publisher=Landes Bioscience|language=en}}</ref> present at the [[N-terminal end|N-terminus]] (or occasionally nonclassically at the [[C-terminal end|C-terminus]]<ref name=":0">{{cite journal |last1=Owji |first1=Hajar |last2=Nezafat |first2=Navid |last3=Negahdaripour |first3=Manica |last4=Hajiebrahimi |first4=Ali |last5=Ghasemi |first5=Younes |title=A comprehensive review of signal peptides: Structure, roles, and applications |journal=European Journal of Cell Biology |date=August 2018 |volume=97 |issue=6 |pages=422–441 |doi=10.1016/j.ejcb.2018.06.003|pmid=29958716 |s2cid=49612506 }}</ref> or internally) of most newly synthesized [[proteins]] that are destined toward the [[secretory pathway]].<ref>{{cite journal | vauthors = Blobel G, Dobberstein B | title = Transfer of proteins across membranes. I. Presence of proteolytically processed and unprocessed nascent immunoglobulin light chains on membrane-bound ribosomes of murine myeloma | journal = The Journal of Cell Biology | volume = 67 | issue = 3 | pages = 835–51 | date = December 1975 | pmid = 811671 | pmc = 2111658 | doi = 10.1083/jcb.67.3.835 }}</ref>
These proteins include those that reside either inside certain organelles (the [[endoplasmic reticulum]], [[golgi apparatus|Golgi]] or [[endosomes]]), secreted from the cell, or inserted into most cellular membranes. Although most [[Transmembrane protein#Classification by Topology|type I]] [[Transmembrane protein|membrane-bound proteins]] have signal peptides, most [[Transmembrane protein#Classification by Topology|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. They are a kind of [[target peptide]].