A transmembrane protein is an integral membrane protein that spans from the internal to the external surface of the biological membrane or lipid bilayer in which it is embedded.

Extraction of a transmembrane protein in the absence of a detergent will result in aggregation and precipitation of the protein.

A hydrophobic domain of the protein resides in the oily core of the membrane, while hydrophilic domains protrude into the watery environment inside and outside the cell or compartment. Transmembrane proteins often have their N-terminal on the exoplasmic face and their C-terminal on the cytoplasmic face. Many transmembrane proteins have multiple membrane spanning alpha helix segments which anchors them to the membrane. Most transmembrane proteins have an internal topogenic sequence.

Types

There are two basic types of transmembrane proteins:

1. Single-pass
2. Multi-pass transmembrane proteins have multiple topogenic sequences.

Examples

• Some cell adhesion proteins
• Some receptor proteins
• Glycophorin
• Insulin receptor
• GLUTI
• Integrin
• Cadherin

See also: membrane topology, transmembrane helix, membrane protein