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.