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. 2012 Jan 20;109(6):1949-1954. doi: 10.1073/pnas.1105266109

Fig. 2.

Fig. 2.

TFIIH complexes. Class averages (Upper) and RCT reconstructions (Lower) of TFIIH complexes. (A) Minimal core, lacking Rad3. (B) Core, with additional density revealing the location of Rad3. (C) Unfixed core + Ssl2 data with additional density revealing the location of Ssl2 in several conformations indicating the flexibility of the Ssl2 subunit. (D) Fixed holoTFIIH with additional density revealing the location of the TFIIK kinase trimer. (E) Fixed holoTFIIH with Tfb3-calmodulin-Au (holoTFIIH+gold), indicating location of the TFIIK kinase trimer. In gold is shown the inverse volume corresponding to the negative density attributed to the gold particle attached to calmodulin bound to the CBP at the C terminus of Tfb3. Density that appears to be a connection between the trimer and the top of Rad3 is presumably due to Tfb3. RCT reconstructions were low-pass filtered to 35 Å and thresholded to match predicted volumes based on molecular weights (Table S4). The number of particles used to produce each class average and 3D reconstruction is indicated. The class average for fixed holoTFIIH has a less distinct appearance possibly due to inferior staining caused by residual glycerol or variability in cross-linking, because this dataset was obtained from a preparation isolated on a glycerol gradient containing glutaraldehyde. The class average for fixed holoTFIIH+gold has an improved appearance due to extensive washing of the grid to remove glycerol prior to staining. Scale bar, 10 nm (applies to all class averages and reconstructions in Figs. 2 and 3). (F) Fitting of RCT reconstructions. Panel 1 shows the minimal core volume fitted into the core volume, revealing the extra density for Rad3. Panel 2 shows the core volume fitted into one of the fixed core + Ssl2 volumes, revealing the extra density for Ssl2. Panel 3 shows the core volume fitted into the holoTFIIH volume. Panel 4 shows one of the fixed core + Ssl2 volumes fitted into the holoTFIIH volume, showing the extra density for the TFIIK kinase trimer. Fixed core + Ssl2 volumes are shown in F rather than unfixed volumes as in C for consistency with the fixed holoTFIIH in F.