Main Categories
Membrane proteins can be divided into several categories:
- Integral membrane proteins which are permanently bound to the lipid bilayer
- Peripheral membrane proteins that are temporarily associated with lipid bilayer or with integral membrane proteins
- Lipid-anchored proteins bound to lipid bilayer bound through lipidated amino acid residues
In addition, pore-forming toxins and many antibacterial peptides are water-soluble molecules, but undergo a conformational transition upon association with lipid bilayer and become reversibly or irreversibly membrane-associated.
A slightly different classification is to divide all membrane proteins to integral and amphitropic. The amphitropic are proteins that can exist in two alternative states: a water-soluble and a lipid bilayer-bound. The amphitropic protein category includes water-soluble channel-forming polypeptide toxins, which associate irreversibly with membranes, but excludes peripheral proteins that interact with other membrane proteins rather than with lipid bilayer.
Read more about this topic: Membrane Protein
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