Photo-induced crosslinking uncovers an antiparallel strand orientation in heterodimeric (EIAALEK) 3 /(KIAALKE) 3 and (EIAALEK) 3 /(RIAALRE) 3 coiled-coil systems.

We describe for the first time the co-existence of the parallel and antiparallel conformation of the heterodimeric E3/K3 and E3/R3 coiled-coil systems in solution. The introduction of a furanylated amino acid in the (EIAALEK) 3 sequence allowed, upon photo-induced covalent crosslinking, freezing of the respective coiled-coil complexes present in solution. The occurrence of both parallel and antiparallel conformations in solution was supported by computational simulations and further confirmed by fluorescence experiments based on pyrene-pyrene stacking.