Extended Data Fig. 4: Negative-stain EM of TNKS2 SAM shows a two-start helix.
From: Structural basis of tankyrase activation by polymerization
a, Crop of a representative negative-stain electron micrograph (of 67) showing TNKS2 SAM filaments. b, 3D map of TNKS2 SAM alone (left) and rigid-body fitted with the SAM domain from the SAM-PARP model (right). c, Comparison between a 2D class average, a projection of the SAM domain filament 3D map from b, a projection of the SAM domain from the SAM-PARP model, and a projection of the single-stranded TNKS2 SAM DH902/924RE filament crystal structure (PDB ID 5JRT4); scale bars, 50 Å. The features of both the 2D class average and the projection of the 3D map obtained for TNKS2 SAM show clear similarity to those of the two-start SAM domain helix from the SAM-PARP model, as opposed to the single-start helix from the crystal structure. This demonstrates that the TNKS2 SAM domain autonomously forms two-start helices.
