Protein:protein interactions in the lipid bilayer (Review)

At least four different types of interaction between protein transmembrane helices have been described to date. These include the use of charge-pair interactions that can play a positive or negative role in the assembly of multi-subunit complexes such as the T cell receptor, or recruit signal transducing accessory molecules in the case of some Fc receptors. Inter-helix hydrogen bonds have been shown to play an important role in the constitutive activation of certain proto-oncogenes, whereas helix:helix interfaces stabilized solely by van der Waals contacts mediated by non-polar residues also exist. The fourth type of interaction is an inter-chain disulphide linkage which is dependent on a buried charged residue. A role for glycine residues in several of these mechanisms is also suggested. In addition, the use of disulphide mapping to further explore protein:protein interactions within the lipid bilayer is discussed.