חלבונים טרנס-ממברנליים במעבר יחיד

Transmembrane proteins are embedded in the lipid bilayer and have domains on either side of the membrane in addition to their transmembrane domains. They constitute about 25% of the proteins coded in the human genome and have various roles, including transporters, enzymes, and receptors.

The transmembrane domain, the membrane-spanning region of the protein, contains non-polar amino acids that form hydrophobic sections. In contrast, the cytosolic and exoplasmic domains are often hydrophilic.

Depending on the number of times the polypeptide chain crosses the membrane, transmembrane proteins can be classified as either single-pass or multi-pass proteins.

A single-pass protein contains approximately 20 to 30 non-polar amino acid residues spanning the membrane. This pass is most often an alpha-helix positioned vertically or slanted in the membrane.

In an alpha helix, the carbonyl and amide groups in the peptide backbone form hydrogen bonds, while the non-polar side groups point outwards into the hydrophobic environment of the membrane.

Single-pass proteins may form homo- or hetero-oligomers through non-covalent interactions.