Integral membrane protein

Such proteins can only be separated from the membranes by using detergents, nonpolar solvents, or sometimes denaturing agents.

Three-dimensional structures of ~160 different integral membrane proteins have been determined at atomic resolution by X-ray crystallography or nuclear magnetic resonance spectroscopy.

Search integral membrane proteins in the PDB (based on gene ontology classification) IMPs can be divided into two groups:[citation needed] The most common type of IMP is the transmembrane protein, which spans the entire biological membrane.

[4] Integral monotopic proteins are permanently attached to the cell membrane from one side.

[8] As an example of the relationship between the IMP (in this case the bacterial phototrapping pigment, bacteriorhodopsin) and the membrane formed by the phospholipid bilayer is illustrated below.

In this case the integral membrane protein spans the phospholipid bilayer seven times.

E, extracellular space ; P, plasma membrane ; I, intracellular space
Group I and II transmembrane proteins have opposite orientations. Group I proteins have the N terminus on the far side and C terminus on the cytosolic side. Group II proteins have the C terminus on the far side and N terminus in the cytosol.
Schematic representation of the different types of interaction between monotopic membrane proteins and the cell membrane : 1. interaction by an amphipathic α-helix parallel to the membrane plane (in-plane membrane helix) 2. interaction by a hydrophobic loop 3. interaction by a covalently bound membrane lipid ( lipidation ) 4. electrostatic or ionic interactions with membrane lipids ( e.g. through a calcium ion)