Propeller loop
conformations in the experimental structures of
Htel topologies (model 1 is shown for the NMR structures). The GQs
are shown in cartoon, while the propeller loop nucleosides are shown
in sticks. In the TTA propeller loop, PT1, PT2, and PA3 (see abbreviations
in Methods) are colored in green, yellow, and blue, respectively.
In GQs where the PA3 formed alignment with the flanking base, the
flanking base is shown in red sticks. The PDBs of the structures are
(a) 1KF1, (b) IK8P, (c) 2HY9, (d) 2JSM, (e) 2GKU, (f) 2JPZ, (g) 2JSL, and (h) 2MBJ. The a-b, c-e, f-g,
and h show various parallel-stranded, hybrid-1, hybrid-2, and antiparallel
(2+2) GQs, respectively. The propeller loops and 5′ and 3′
ends of GQs are labeled in the figure. Chains 1 and 2 are also labeled
in bimolecular parallel-stranded GQ.