Amphitropic proteins

Most important for the regulation of the membrane architecture are membrane potential, intracellular Ca2+ concentration, pH, changes in lipid composition due to the action of phospholipases and cell-cell coupling as well as the coupling of the membrane to the cytoskeleton and the extracellular matrix. Membrane architecture is additionally modulated by ions, lipo- and amphiphilic hormones, metabolites, drugs, lipid-binding peptide hormones, and amphitropic proteins [44]. 

Involvement of Basic Amphiphilic a-helical Domain in the Reversible Membrane Interaction of Amphitropic Proteins Structural Studies by Mass Spectrometry, Circular Dichroism, and Nuclear Magnetic Resonance... 

A specific phospholipid requirement has been determined for optimum in vitro reconstitution of function for more than 50 membrane proteins. If one considers specific lipid requirements for membrane association and activation of amphitropic proteins, the number is in hundreds. Integral membrane proteins fold and exist in a very complex environment and have three modes of interaction with their environment. The extramembrane domains are exposed to the water milieu, where they interact with water, solutes, ions, and water-soluble proteins. Part of the protein is exposed to the hydrophobic-aqueous interface region (Fig. 9). The remainder of the protein is buried within the approximately 30-A thick hydrophobic interior of the membrane. Amphitropic proteins may spend part of their time completely in the cytosol and are recruited to the membrane surface, or even partially inserted into the membrane, in response to various signals. 

Three structure-specific domains, mostly found in eukaryotic cells, have been identified for membrane association and activation of amphitropic proteins [21]. The Cl lipid clamp is a conserved cysteine-rich protein domain that binds lipids and is found in protein kinases... 

In prokaryotic cells, the protein structural features defining lipid-binding domains are less well conserved than in eukaryotes, and the membrane ligand appears to be an anionic lipid-rich domain with little selectivity for the chemical species of lipid. DnaA (K. Boeneman, 2005), MinD [20], and SecA (Section 5.3) are amphitropic proteins in... 

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