# Topogenic sequence
> Mediated Wiki article. Canonical URL: https://mediated.wiki/source/Topogenic_sequence
> Markdown URL: https://mediated.wiki/source/Topogenic_sequence.md
> Source: https://en.wikipedia.org/wiki/Topogenic_sequence
> Source revision: 1150304704
> License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/)
A '''topogenic sequence''' is a collective term used for a [peptide sequence](/source/peptide_sequence) present at nascent proteins essential for their insertion and orienting in [cellular membranes](/source/cell_membrane). The sequences are also used to translocate proteins across various intracellular membranes,[{{cite journal|last=Robinson|first=A|date=1 September 1987|title=The role of topogenic sequences in the movement of proteins through membranes.|journal=Biochem. J.|volume=246|issue=2|pages=249–261|author2=Austen, B|doi=10.1042/bj2460249|pmid=3318806|pmc=1148271}}] and ensure they are transported to the correct organelle after synthesis.[{{cite journal|last=Gould|first=Sven|date=June 2008|title=Plastid Evolution|journal=Annual Review of Plant Biology|volume=59|pages=491–517|doi=10.1146/annurev.arplant.59.032607.092915|pmid=18315522|author2=Waller, R|author3=McFadden, G}}] The position of the sequence may be at the end, e.g. N-terminal signal sequence, or in mid parts of the nascent protein, e.g. stop-transfer anchor sequences and signal-anchor sequences.[{{Cite book|title=Molecular Cell Biology|last=Lodish|first=Harvey|publisher=Macmillan Higher Education|year=2013|isbn=978-1-4292-3413-9|location=|pages=587–588}}] If the sequence is at the end of the polypeptide, it is cleaved off after entering the ER-lumen (via a translocon) by a signal peptidase, and subsequently degraded.
As an example, the vast majority of all known complex plastid [preproteins](/source/preproteins) (an 'unactivated' protein) encoded in the nucleus possess a topogenic sequence.