![cover image](https://wikiwandv2-19431.kxcdn.com/_next/image?url=https://upload.wikimedia.org/wikipedia/commons/thumb/d/db/Polytopic_membrane_protein.png/640px-Polytopic_membrane_protein.png&w=640&q=50)
Single-pass membrane protein
Transmembrane protein / From Wikipedia, the free encyclopedia
A single-pass membrane protein also known as single-spanning protein or bitopic protein is a transmembrane protein that spans the lipid bilayer only once.[1][2] These proteins may constitute up to 50% of all transmembrane proteins, depending on the organism, and contribute significantly to the network of interactions between different proteins in cells, including interactions via transmembrane alpha helices.[3] They usually include one or several water-soluble domains situated at the different sides of biological membranes, for example in single-pass transmembrane receptors. Some of them are small and serve as regulatory or structure-stabilizing subunits in large multi-protein transmembrane complexes, such as photosystems or the respiratory chain. A 2013 estimate identified about 1300 single-pass membrane proteins in the human genome.[4]
![Thumb image](http://upload.wikimedia.org/wikipedia/commons/thumb/d/db/Polytopic_membrane_protein.png/320px-Polytopic_membrane_protein.png)
The membrane is represented in yellow.