Fig 4. Schematic representation of the quaternary structure of the K/E heterodimer and K homodimer, both in parallel arrangement.

K- and E-peptides are shown as cylinders in grey and black color respectively. Red circle represents the spin-label position. (a) K/E heterodimer, with the N-terminus of K- and the C-terminus of E-peptide spin labelled, while in case of (b), the C-terminus of both peptides are spin labelled. (c) and (d): parallel K homodimers. (c) K-peptide labelled at the N-terminus, (d) at the C-terminus. (e) shows schematically the distance between two spin labels in case of the parallel K/E-heterodimer where the N-terminus of K- and the C-terminus of E-peptide is spin labelled (situation (a)).