Which types of amino acid interfaces can support TMD-TMD interaction?

Background:

Interactions between transmembrane domains (TMDs) rely on helix/helix interfaces built from specific amino acid motifs. It is currently unclear how many different motifs exist and which types of physical forces they employ.

The concept:

One approach to identify novel interfacial motifs is to generate libraries of TMDs with random primary structure and use a selection method in model organisms such as Escherichia coli, to select self-interacting sequences. Selected TMDs with strong affinity can then be characterized by scanning mutagenesis to identify novel interfacial motifs that facilitate the TMD-TMD interaction.