Fig. 3: Unique conformations of KASH6 peptides within the SUN1-KASH6 structure.
a–c Alternative conformations adopted by KASH6 peptides and their associated SUN domain KASH-lids for (a) KASH6α, (b) KASH6β and (c) KASH6γ. d–f Superposition of the KASH peptide and its associated SUN1 protomer from previous crystal structures of SUN1-KASH1 (green; PDB accession 6R15)37, SUN1-KASH4 (brown; PDB accession 6R16)37 and SUN1-KASH5 (purple; PDB accession 6R2I)37, with (d) SUN1-KASH6α (red), (e) SUN1-KASH6β (blue) and (f) SUN1-KASH6γ (yellow). d KASH6α follows the same initial path, undergoing β-interaction with its canonically-oriented KASH-lid, as in all previous SUN1-KASH structures. It then hooks below KASH-lidα, undergoing a 90° bend to form an α-helix that is oriented in the opposite direction to the partial α-helical end of KASH1. e KASH6β forms the same β-interaction with its KASH-lid as in all other SUN1-KASH structures, but with an unusually high angulation of both KASH6β and KASH6-lidβ. f KASH6γ was only observed as three amino-acids at the KASH-binding pocket, with partial occupancy, and in only a subset of crystal structures. In absence of the β-interaction, its KASH-lid adopts a low angulation in which its first β-strand overlays with the KASH-lid-interacting β-strand of other KASH peptides.
