Self-assembling peptide surfactants A₆K and A₆D adopt α-helical structures useful for membrane protein stabilization

Elucidation of membrane protein structures have been greatly hampered by difficulties in producing adequately large quantities of the functional protein and stabilizing them. A₆D and A₆K are promising solutions to the problem and have recently been used for the rapid production of membrane-bound G protein-coupled receptors (GPCRs). We propose that despite their short lengths, these peptides can adopt α-helical structures through interactions with micelles formed by the peptides themselves. These α-helices are then able to stabilize α- helical motifs which many membrane proteins contain. We also show that A₆D and A₆K can form β-sheets and appear as weak hydrogels at sufficiently high concentrations. Furthermore, A₆D and A₆K together in sodium dodecyl sulfate (SDS) can form expected β-sheet structures via a surprising α-helical intermediate.