Single-pass membrane protein

[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.

[4] 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.

The transmembrane domain is the smallest at around 25 amino acid residues and forms an alpha helix inserted into the membrane bilayer.

[10] Some proteins in this class function as monomers, but dimerization or higher-order oligomerization is common.

[12] The fraction of proteins in this class is larger in humans than in the model organisms Danio rerio (zebrafish) and Caenorhabditis elegans (nematode worms), suggesting that genes encoding these proteins have undergone expansion in the vertebrate and mammalian lineages.

Schematic representation of transmembrane proteins: 1. a protein with single transmembrane α-helix (a single-pass membrane protein) (bitopic) 2. a polytopic transmembrane α-helical protein 3. a polytopic transmembrane β-sheet protein
The membrane is represented in yellow.