1. Crystal Structure of an Octameric RuvA–Holliday Junction Complex
S.Mark Roe, Tom Barlow, Tom Brown, Mark Oram, Anthony Keeley, Irina R Tsaneva, Laurence H Pearl 
Molecular Cell 
Volume 2, Issue 3, Pages (September 1998)
DOI: /S (00)

2. Figure 1 Structure of M. leprae RuvA Monomer
Secondary structure cartoon of the M. leprae RuvA monomer, colored from the amino terminus (blue) to the carboxyl terminus (red). Segments of the polypeptide for which no interpretable electron density is visible are indicated as broken magenta lines.
Molecular Cell 1998 2, DOI: ( /S (00) )

3. Figure 2 Structure of M. leprae RuvA Octamer
(a) Arrangement of tetramers (shown as green and magenta) in the M. leprae RuvA octamer.
(b) Arrangement of domains within the tetramers. The polypeptide chains are colored as in Figure 1. The center of each tetramer is formed by the N-terminal β domain (blue-cyan), the edges by the central helix-hairpin-helix domain (green-yellow), and the corners by the C-terminal three-helix bundle domain (orange-red).
(c) As (b) but viewed as in (a).
(d and e) Symmetry of the arrangement of the monomers within the octamer. Sets of monomers related by the local pseudosymmetry have the same color. Positions of the local two-fold axes relating North to South, East to West, and Up to Down subunits within the octamer are indicated.
Molecular Cell 1998 2, DOI: ( /S (00) )

4. Figure 3 Octamer Protein–Protein Interface
(a) The helix pairs that form the four protein–protein interfaces connecting the tetramers in the octamer are highlighted, with those from A chains in gold and those from B chains in blue.
(b) Detail of the side chains along the helices from 118 to 129, which are involved in ion pair and hydrophobic interactions in the tetramer–tetramer interface. Basic side chains are shown in blue, acidic in red, and hydrophobic in green.
(c) Alignment of amino acid sequence for the equivalent helices to that at 118–129 in the M. leprae RuvA, from gram-negative bacteria (E. coli, H. influenzae, H. pylori, and P. aeruginosa), and one gram-positive bacterium (B. subtilis).
Molecular Cell 1998 2, DOI: ( /S (00) )

5. Figure 4 Cruciform Cavern
Surface picture of the cruciform cavern generated by the octameric protein shell of M. leprae RuvA. The protein surface has been transected through the center of gravity of the complex, in the Up–Down/East–West plane, and is viewed from the North. The surface is colored according to the distance from the center of gravity, going from red (closest) to blue (farthest). The stalagmite–stalactite structure formed by the side chains of the eight copies of Glu-54 can clearly be seen (in red) constricting the height of the cavern at its center.
Molecular Cell 1998 2, DOI: ( /S (00) )

6. Figure 5 Structure of the Bound Holliday Junction
(a) Stereo pair showing the electron density (blue surface) from an Fo − Fc difference Fourier with calculated structure factor amplitudes and phases deriving only from the refined protein shell. The image shows a 20 Å thick slab of the difference Fourier, centered at the center of gravity of the octameric protein shell and contoured at 1.25 σ, and is viewed from the Up direction. Shown in red are the side chains of Glu-54 from the eight protein subunits that form the stalactite–stalagmite around which the DNA splits.
(b) Stereo pair showing a detailed view of the difference Fourier electron density (calculated as in [a]) in the North arm of the cavern. The strongly scattering planes of the bases and the phosphate groups of the backbone can be clearly seen. A symmetrized DNA duplex is shown superimposed on the density, with the sugars and bases colored blue, and the phosphates red. The secondary structures of the different tetramers are colored magenta or green, as in Figure 2A.
(c and d) Details of the loops in the HhH motifs at 112–118 (c) and 77–83 (d), which interact with the phosphate backbone of the same strand.
(e) Overall view of the interactions made by one strand of the DNA with the HhH motifs from different tetramers (shown in yellow).
Molecular Cell 1998 2, DOI: ( /S (00) )

7. Figure 6 Strand Crossover
Stereo pair showing the electron density from a difference Fourier phased on protein only (see Figure 5), for the crossover at the North–West inner corner of the cruciform cavern. The loops of the HhH motifs from the Up and Down tetramers, which interact with the phosphates at the beginnings of North and West arms respectively, are shown in yellow.
Molecular Cell 1998 2, DOI: ( /S (00) )

8. Figure 7 RuvA as the Stator for the RuvB Motor
(a) Schematic diagram of the proposed RuvAB branch migration complex based on Parsons et al. 1995a. In the “unstable” form with only one RuvA tetramer bound, the torque generated by the counterrotating RuvB motors would cause the RuvA tetramer to rotate around its own axis, disrupting interactions with DNA. In the “stable” form with the RuvA octamer described here, the twisting of one RuvA tetramer is opposed by the counter motion of the other tetramer, stabilizing the complex for branch migration. In a putative RuvABC resolution complex, interactions between a RuvC dimer and RuvB motors might provide sufficient stability for limited branch migration even when only one RuvA tetramer is bound.
(b) Space-filling picture of the M. leprae RuvA octamer shell. The C-terminal domains (in red), which are essential for RuvB interactions, are arrayed on either side of the mouths of the tunnels.
Molecular Cell 1998 2, DOI: ( /S (00) )