PROTEIN PROTEIN INTERACTIONS IN THE LIPID BILAYER (REVIEW)/

At least four different types of interaction between protein transmemb rane helices have been described to date. These include the use of cha rge-pair interactions that can play a positive or negative role in the assembly of multi-subunit complexes such as the T cell receptor, or r ecruit signal transducing accessory molecules in the case of some Fc r eceptors. Inter-helix hydrogen bonds have been shown to play an import ant role in the constitutive activation of certain proto-oncogenes, wh ereas helix:helix interfaces stabilized solely by van der Waals contac ts mediated by non-polar residues also exist. The fourth type of inter action is an inter-chain disulphide linkage which is dependent on a bu ried charged residue. A role for glycine residues in several of these mechanisms is also suggested. In addition, the use of disulphide mappi ng to further explore protein:protein interactions within the lipid bi layer is discussed.