Six amino acids define a minimal dimerization sequence and stabilize a transmembrane helix dimer by close packing and hydrogen bonding.

Distinct amino acid sequences have been described to mediate oligomerization of transmembrane α-helices. However, as the sequence context is crucial to determine specificity in transmembrane helix-helix interaction, the question arises how small a sequence can be without losing specificity. In the present analysis, six amino acids have been identified in the PsbF transmembrane helix dimer, which form the contact region of two interacting helices and are directly involved in helix-helix interactions. However, individual amino acids within the complex sequence pattern only together ensure sequence specificity of the analyzed transmembrane helix-helix interactions by mediating close packing and inter-helical hydrogen bonding.