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Figure 11
Helix α2 connects the two interfaces. A superposition of the SEPT3G–GMPPNP complex (light blue) with SEPT3α0G–GDP (dark blue) and SEPT9GC–GDP (dark green) in the region of switch II, helix α2 and the sep2 motif. Helix α2 traverses the molecule from one interface to the other. Phe129 (SEPT3 numbering) is shown. All molecules bound to a GTP analogue show this phenylalanine in the buried position (light blue), whilst the GDP complexes show much variation, with examples of all three of the conformations shown. The sep2 motif lies underneath α2 such that it does not make conventional packing contacts with the underlying β-sheet. α2 may be a means to transmit structural information from the G interface to the NC interface once switch II is released after GTP hydrolysis.

IUCrJ
Volume 7| Part 3| May 2020| Pages 462-479
ISSN: 2052-2525
https://doi.org/10.1107/S2052252520002973