A posteriori design of crystal contacts to improve the X-ray diffraction properties of a small RNA enzyme

MacElrevey, C.; Spitale, R.C.; Krucinska, J.; Wedekind, J.E.

doi:10.1107/S090744490702464X

Figure 6
Schematic surface and ball-and-stick diagrams illustrating a pseudo-four-way helical junction generated by crystal-packing interactions of minimal hairpin ribozymes. (a) Unit-cell perspective of the twofold and 2₁-fold symmetry contacts within the asymmetric units of both C3L and S9L structures. Superposed C3L (blue) and S9L (magenta) molecules are shown overlaid in the center of the diagram (i.e. reference molecule). The minimal difference in the lengths of the a and b axes of the C3L and S9L unit cells (3.2 Å) allows greater conservation in the superposition as it is extended from the reference molecule's asymmetric unit; therefore, symmetry-related S9L molecules (pink surface representations) are largely hidden behind the C3L molecules (blue and green cartoon and stick depiction). Helix H1 is labeled to demonstrate its high degree of solvent exposure. The 2₁ screw axis depicts the relationship between H3 and H4′. The boxed region is expanded in (b)–(d). (b)–(d) Individual panels of the junction region of the C3L, S9L and 4WJ structures. Residues are colored according to strand conventions in Fig. 1

(b) and numbered according to hairpin-ribozyme conventions (Chowrira & Burke, 1991

). Surface representations for the C3L molecules are coloured as observed in (a) and rotated 90° anticlockwise from that perspective. O atoms engaged in putative hydrogen bonds are designated as red spheres connected by dashed lines.

BIOLOGICAL
CRYSTALLOGRAPHY

ISSN: 1399-0047

Volume 63| Part 7| June 2007| Pages 812-825

doi:10.1107/S090744490702464X

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